Wix Stores: Is it Possible to have Multiple Shipping Methods?

Hi, I have flat shipping rates based on the amount purchased using FedEx. It only becomes free if the amount purchased is over $150.
But, I also sell Gift Certificates and very small items that can be mailed via USPS with just a postage stamp. Is it possible to make these small items have free shipping with no regard to their price? Possibly via Corvid?
I have read through all the documentation I can find and I can’t seem to find an answer.
Thanks in advance!