Refrigerate pizza so slices will separate cleanly.
Stack slices 3 each.
Wrap 3-slice stack in foil.
Seal foil-wrapped stack in Ziploc back.
Wrap 2-3 ziplock bags (that is, 2-3 stacks of slices) together in bubble wrap, put in a cardboard box, more bubble wrap, mark "perishible." Check curbside (so it goes straight to the plane and stays cold, if they do it that way) and pray for the best.