I have been using the "first class mail parcel" option and selecting package/thick envelope to send 5x9 bubble envelopes.
I now have a large quantity of items that measure 10x10. My question- are there any restrictions on the size or shape of an envelope when choosing the "first class mail parcel" pkg/thick envelope option?
The First Class Parcel is for thick envelopes AND packages (which would include boxes). Your dimensions are not anywhere near the limits of being an oversized package.
P.S. It would be hard to make an oversize package without going over the 13 ounce limit for first class mail.
