Minted all in one invitations, how did you seal them?

I found invites I like from minted for a really reasonable price, they are "all in one" so it unfolds and you have the invite and the rvsp tears off for the guest to send back as a post card style RSVP card, anyways I bought a wax seal kit from Amazon and I tested it out on some sample cards and they rip when you open it, i saw wax seals you can buy that have adhesive on the back that I am considering but not sure how they work, im not sure how else i would seal these invitations unless I change the style any advice appreciated.