How to eat it – Making a sandwich:^[1] 

One is required to eat the Matzah and Maror together in a form known as Kericha, which is a wrap [and today as a modern day sandwich]. [Originally, before the advent of hard matzah, when matzot were soft and pliable like laffa, korech was performed as an actual wrap, similar to a tortilla or shawarma wrapped in laffa. However, with the widespread adoption of hard matzah over the past roughly three hundred years^[2], it became impractical, if not impossible, to form a true wrap, as the matzah could no longer bend without breaking. As a result, the sandwich method developed, serving as the closest possible substitute for the original act of kericha. At the same time, we find an interesting debate among the Rishonim regarding the original form of the wrapping, namely whether the maror was wrapped around the matzah or the matzah was wrapped around the maror, as will be explained next.]

What wraps what – The Matzah wraps the Maror or the Maror wraps the Matzah: Many Rishonim^[3] explicitly describe that the maror wraps around the maror, and so is the ruling according to Kabbalah of the Arizal.^[4] Indeed, so is the widespread custom amongst some Sephardic communities, including the tradition of Yemenite and Tunisian Jewry even today.^[5] Other Rishonim^[6] however describe that the matzah should wrap the maror. According to these views, the maror encloses the matzah rather than the other way around. Indeed, the most widespread custom among Ashkenazim, and indeed among most Sephardim as well[7], follows this view to wrap the matzah around the maror, meaning to place the maror between two pieces of matzah and form a sandwich. Practically, each community follows its accepted custom; however, one should not suffice with merely placing the maror on top of the matzah and eating them as a stack. Rather, one should specifically form a sandwich, as this most closely reflects the concept of a wrap, and it is possible that one does not fulfill the obligation of korech at all when this element is lacking.[8]

[1] Admur 475:15-21; 26-27; Siddur Admur regarding Korech “Wrap them together and say and eat them together”; Michaber ibid; Tur 475; Rambam Chametz Umatzah 8:6; Pesachim ibid “Hillel would wrap them together and eat them”; Rashbam Pesachim ibid “He would wrap the Pesach Matzah and Maror in one wrap, such as one who wraps something with a rubberband”; Sefer Hapardes Shaar Hamaaseh; Rabbenu Chananel Pesachim ibid; Sefer Hamanhig Hilchos Pesach 84; Maharach Or Zarua 21; Rif Geios Pesachim 334; Iggur Hiulchos Leil Pesach 813; Sefer Hachinuch Mitzvah 21; Seder Hayom; Maggid Mishneh on Rambam ibid in name of Maharitz Geios p. 102; Peri Eitz Chaim Shaar Chag Hamatzos; Hagadah Ish Matzliach Erech Koreich p. 62 that so is their custom; Maharitz in Tachliel Etz Chaim 2 in name of Rashbam and Rebbe Yitzchak Bne Geios and Michaber in Maggid Meisharim; Bayit Neman Vol. 57; Chazon Ovadia Pesach p. 100; Kitzur Yalkut Yosef 2:75; Arichas Hashulchan 6:95; Shulchan Aruch Hamekutzar Ratzabi 3:91; Toras Hamoadim Yosef 25:1; Yalkut Yosef Moadim 473:11 that so is the Sephardic custom; Hagadah Ish Matzliach Erech Koreich p. 62 that Minhag Ashkenaz is to make a sandwich; Bayit Neman Vol. 57; Halichos Hamoed [Malka] Koreich p. 343

See regarding the use of the term Korech and Kericha and that it means to wrap: Admur 25:15 and 24; 27:12; 32:69; 328:53; 331:9

[2] See Admur Shut 6; Shaareiy Teshuvah 461; Ashel Avraham Butchach 461; M”B 461:10; Piskeiy Teshuvos 461:10

[3] Rabbenu Chananel Pesachim ibid; Sefer Hamanhig Hilchos Pesach 84; Iggur Hiulchos Leil Pesach 813; Sefer Hachinuch Mitzvah 21; Seder Hayom; Maggid Mishneh on Rambam ibid in name of Maharitz Geios p. 102; Hagadah Ish Matzliach Erech Koreich p. 62 that so is their custom; Maharitz in Tachliel Etz Chaim 2 in name of Rashbam and Rebbe Yitzchak Bne Geios and Michaber in Maggid Meisharim; Bayit Neman Vol. 57; Chazon Ovadia Pesach p. 100; Kitzur Yalkut Yosef 2:75; Arichas Hashulchan 6:95; Shulchan Aruch Hamekutzar Ratzabi 3:91; Toras Hamoadim Yosef 25:1

[4] Peri Eitz Chaim Shaar Chag Hamatzos

[5] Hagadah Ish Matzliach Erech Koreich p. 62; Bayit Neman Vol. 57; Shoel Umeishiv 8:80

[6] Maharach Or Zarua 21; Rif Geios Pesachim 334

[7] Yalkut Yosef Moadim 473:11 that so is the Sephardic custom; Hagadah Ish Matzliach Erech Koreich p. 62 that Minhag Ashkenaz is to make a sandwich; Bayit Neman Vol. 57; Halichos Hamoed [Malka] Koreich p. 343

[8] Despite all of the above explanations regarding the meaning of the term kericha, one can argue, based on the discussions found among the Poskim, that the primary intent of korech according to Hillel is that the matzah and maror be eaten together. Accordingly, even if one does not form a full wrap or sandwich, but eats them together in a simpler manner—such as placing the maror on top of the matzah, or even holding each in a separate hand and eating them simultaneously—although this departs from the original form and intent of kericha, it may nevertheless be argued that the mitzvah has technically been fulfilled. On the other hand, one may argue that wrapping is not merely an ideal enhancement but an essential component of the mitzvah itself, as indicated by the repeated and deliberate use of the term kericha by Chazal and the Poskim. According to this view, the foods must be physically wrapped and eaten as a single unified entity, and one who merely places one food on top of the other without forming a wrap or sandwich has not fulfilled the mitzvah of korech at all, as the defining element of wrapping is lacking.