I have an HP Envy Inspire 7255e. It’s smallest supported page size is 4x6. Today I wanted to print on 3x5 index cards. In order to accomplish this I took a 4x6 index card and cut some angled slices into it with a razor blade, then inserted the smaller card into the slices on the larger card.
Hopefully the image below illustrates this. The cuts I made are highlited in the image below.
I set my document size to 4x6 inches and then increased the margins to accomodate.
This creates lots of extra edges on the page and that makes printer jams more likely. It works for me but your mileage may vary. This could even damage the printer. You’ve been warned.