Couple things in response to a few posts above. Making these would be an experiment in cost effectiveness. I had the same thought.. $6 per 90 ain't too bad... About the cost of some paper targets bought in bulk.
Can't use steel targets at this range. Paper only in the regular 50/100 yrd areas. The gravel/mud plinking pit you can place old plastic bottles, boxes etc. No glass, no metal. They use clays, and also have throwers mounted for shot gun fun (in addition to a dedicated trap range area).
People do use food stuffs(melons, pumpkins, marshmallows, whatever) so that's not a problem, but neither is the debris left from clays. The pit is.. well... Kind of a pit, lol.
Bowling pins would be good, but unless you go back down into the muddy pit to retrieve them....
I have a small supply of cardboard tubes, about 7" diameter by 11" tall about an inch thick, from work. They are from coils of specialty steel. These will work very nice.
I've found several recipes for kids clay made from salt, baking powder , etc.... But again, how much is any of that going to cost, plus time ( with a little boy, work, and life.. time is the most expensive thing here) , electric for the oven, plus a can of spray paint? And I don't get out to this place very often... So...
Unfortunately it may be smarter to just grab a box from Wally world and not make a whole big production of it. If I was still in CO and shooting in the woods every other day, then I'd be more inclined to pursue this.
We'll see.