I needed something to keep my fishing tackle in on my fishing sup. My father-in-law has a few crates laying around. So I made myself a SUP Fishing Crate. The crate already had a bit of the side removed and this is perfect to get your stuff out without having to lift the lid. I made the seat from a bit of scrap wood and it is really great to have a seat on the fishing sup. Initially I had all the rod holders inside the crate and facing straight up. After a few sessions I found the rods straight up not ideal. So I move them to the outside of the box and put them at a slight angle. The rod holders are made with PVC pipe and attached using cable ties. I use bungie cords to keep the crate attached to the fishing sup.
Here are some pictures of a diy SUP Fishing Crate.