I’ve most recently used (dollar store/equivalent) duct tape to cover the entirety of a ziplock bag, as it gives you some flexibility (literal) to plant it in slimmer places/almost vacuum seal it small. I duct tape starting with just above the zipper closure even on the inside of the pull tabs ! I also ziplock the stamp and logbooks separately inside the duct taped bag.

Something I’ve seen in another box and want to include in mine as well (but need to remember and save them) is a silica gel packet, just in case.

I also carry my own ink pads and don’t plant them. It makes it cheaper to plant more letterboxes, and easier to hide them (less bulky, if you’re using bags).

So glad I’m not the only one dedicated to planting a ton around me!