Put it in a small jar, lift up a stepping stone, dig down put it there. Or, put a couple sticks on the side of your lawn. 2 in a row and where the lines intersect, bury it there. Look where they intersect to find the key.
I used to tie my key to a strong elastic and screw it the inside of my door to the side of the letter box..... Your proberbly thinking 🤔🤔 what if someone saw me getting my key from the letter box, Well they would lose they're fingers or hand Because behind that door would be my boy, a short tempered grumpy Rottweiler & my girl well behaved but suspicious Pitbull...... Even before I put my hand in the letter box to get my key I would have to let them know it was me just by talking so they recognise my voice...... Never once has anyone tried to get into my home....... At least I don't think so, not unless the dogs ate the evidence & cleaned up any blood there might have been 🤣🤣🤣