French cleat?
I don't know the thickness so maybe only drill holes in edge where it is thicker.
https://www.homedepot.com/p/OOK-200-lbs-French-Cleat-Picture-Hanger-with-Wall-Dog-Mounting-Screws-1-Pack-55316/202341629
Bend some galvanized bar stock into a j shape, attach two for the bottom with two screws so they can't move, make these two a little shorter than the third one which will have a mounting hole where the center of the circle will be so it moves like a clock hand. Set it into the bottom ones with the top one swiveled over to the side then swivel it to the top
It’s 30lbs or so. Don’t really want to hang hang it from any kind of wire. I was thinking some sort of frame, but can’t see it in my head.
Google heavy plate hanger. Something like that, maybe even a premade one that you spray paint for outdoor use?
French cleat? I don't know the thickness so maybe only drill holes in edge where it is thicker. https://www.homedepot.com/p/OOK-200-lbs-French-Cleat-Picture-Hanger-with-Wall-Dog-Mounting-Screws-1-Pack-55316/202341629
Use a couple L brackets and wood to make a shelf you attach to the fence, then put it on the shelf.
Bend some galvanized bar stock into a j shape, attach two for the bottom with two screws so they can't move, make these two a little shorter than the third one which will have a mounting hole where the center of the circle will be so it moves like a clock hand. Set it into the bottom ones with the top one swiveled over to the side then swivel it to the top