I don't use a recipe. I've discovered that I don't like the flavor of pork bones in mine (that batch got dumped, it was nasty).
I toss in the carcass/bones, dump in water until it's covered and about an inch below the top of my crock pot, toss in a spoonful or two of lemon juice, turn it on high until it boils, then leave it on low until about the same time the next day.
I cooked it down afterwards last time (reduced it) to about 1/3 of the volume, and it's delicious and takes up much less space in my freezer.