Yosef Karo

“ This is done by putting all of the matzos in a basket, and the basket groups them together with regards to hallah. This is the best way. Rem"a: If the matzo had the minimum quantity for hallah, but one forgot to separate, he should separate afterwards, and the basket grouping is not necessary. ”

“ If one separated from some of the doughs but not from others, and they get mixed together, he must then take hallah from each one individually or knead a new dough and take hallah from it for the ones that were mixed up. ”