Cut and stack 16 pieces of foil to wrap sandwiches; set aside. Carefully break (or cut) graham crackers in half to form squares. Sandwich 1/4 cup of ice cream between 2 graham-cracker squares. Repeat with the remaining graham crackers and ice cream. Wrap the sandwiches in foil and transfer them to an airtight container or resealable plastic bag. Freeze until solid, at least overnight, and up to 1 week ahead.