What is a better base for skid foundation, gravel or crushed stone?
Tamped gravel uniform or not, big or small, rounded or jagged with thin concrete pads (home-made or store bought), retaining wall caps or path pavers set into the gravel. Like doing a walking path really. You can even do a peanut brittle type setup by pouring in a lot of real soupy cement. But, the 4-inch carve-out of the ground you'll do should retain the gravel quite well.