The Jewish people took dough out of Egypt with them. See Shemos 12 (39) which says
“They baked the dough that they had taken out of Egypt as unleavened cakes, for it had not leavened, for they were driven out of Egypt, and they could not tarry, and also, they had not made provisions for themselves.”
and Shemos 12 (34)
“The people picked up their dough when it was not yet leavened, their leftovers bound in their garments on their shoulders.”
when it was not yet leavened: The Egyptians did not permit them to tarry long enough for it to leaven.
their leftovers: The remaining matzah and bitter herbs.
My question is when was this dough made (was it the leftovers of the dough for the matzos that they ate with the korban Pesach).
related - my question last year: How did our forefathers bake the dough they took out of Egypt? Would it qualify as matzo now?