Ryan, posts are pressure treated 4x4 set somewhere between 3.5 to 4 feet in the ground, no concrete (IMO concrete holds moisture and causes the posts to rot faster). I believe I set the posts 24" apart front to back and 8' apart side to center to side. The rafters are 2x4 and the beams that the rafters set on are 2x6. The ends are closed in with a single sheet of plywood so it's 4' deep. I forget what the slope is. It's a bit higher then 8' in the front as the plywood is full height at the front and is up from the ground about 2" to 4". Though with the 2x6 beam, there is less then 8' clearance. Before I stacked any wood in it I folded up a tarp to fit between the posts and laid it down, then placed two 2x4s over the tarp and put two pallets on the 2x4s. The wood was then stacked on the pallets. Two pallets fit perfectly between the posts, yes I planned for that.
Next time I have it open to haul in some wood I'll try to remember to take some photos of the inside.