Years ago I could build these trailers from scrap and sell them ,But in the last few years, Ive found that you can buy them from Home Depot etc way less money.
I broke down and bought one, and its OK. but a bit bumpy riding when empty. One thing to look for is a fill shackle system some will have the real shackle just in a slide pocket of some sort this ads to the noises .
I have 7 trailers now, and the best one is from an older camper trailer, I stripped it down, and put on sides and a PT deck, IT is the smoothest riding trailer I ever had, and a good capacity.
So next to starting from scratch maybe look around for that old trailer and strip it down , that was work, but well worth it.
Oh yes id recommend at least a 12 inch wheel..