Mail it!
My timecard cards are often non-machinable.
Non-machinable mail can not fit through postal machines. The envelopes are either too thick, rigid, padded or have unusual object inside so USPS requires extra postage to hand cancel.
Starting on July 14, 2024, a non-machinable stamp will be worth $1.19 . There will be a 5-cent increase in the price of a First-Class Mail Forever stamp from 68 cents to 73 cents.