I'm doing a flagstone pathway for a customer. Flagstone might be the wrong word. It's the stones that are used to build the flat rock walls. I'm planning on piecing them together like a jigsaw puzzle with 2 to 4 inches in spacing. The walkway will be 3-4 feet wide and 30 feet long. My question is what should I use to fill in the spaces. I was thinking that 2-4 inches might be too much for sand. Would peagravel do the trick? Ideas would be appreciated. thanks.