Well let's just say 6 is a nice workable number.
I may have accumulated a couple of extra pieces of lumber along the way.
When you go to a lot of unknown, not groomed campsites it's hard to have too many. Also, despite having sand pads there's times on sloping sites where you need an extra block or two under the stabilizer.
This site was fun. More fun because of a large contingent of folks watching and ready for some afternoon entertainment. It was the only beach front site available but had a real slope to it. Sized it up, excavated a sand trench on the high side and used an assortment of blocks on the low side. Backed in in one shot. Sorry folks, I hate being other folks entertainment.
It's an example why it's good to have an extra block or two. Without one under the stabilizer it wouldn't have reached the ground.
My blocks are 2 by material but I added a 1/2" plywood on one side for two reasons. One, that makes it high enough that when you back up onto one the other wheel is free to spin. Good for changing tires or adjusting brakes. Two, the layer of plywood prevents the 2 by material from splitting etc.