I built a few racks last year for myself as well. I just used 11/2" x .100 wall square tubing. Real basic design, a rectangle bottom, with rectangle uprights. The same design as the amazon
one above. I attached the whole thing to treated 4x4s cut to 4 '. No top to speak of, I just tarp the top for now but leave it open on the sides so air can flow through. I plan to put a proper sloped tip on with tin to keep the rain off. They seem to be working, my last year wood is looking nice and seasoned.
I'll post some picks when I get back home so.