"I know I'm late to the party, but if you ever need such advice, a moist paper towel can work quite well too. You can also cut out the paper towel into different lengths and shapes and rest food on them for the slime mould to find."
"Whatever it is, it's beautiful, it's probably a crust fungus of some sort, put on some gloves & poke it, if it's hard, it's probably a crust fungus or the Sclerotium of an unusually large slime mold."
It is a very nice picture! I do not think this is a slime mold. Usually if it is a slime mold you can "whipe it off" with your fingers in the plasmodial state. I guess this is a crust fungus. They usually grow on wood logs…"