I built my own rack a couple of years ago. Based on the Hi-Fi racks designs, but using plywood as an alternative for solid wood (for rigidity), and three legs as opposed to four for ease of levelling. I was pleased with there result, but it was (very) time consuming as i’m rather obsessive about paint finish and this took quite an effort!
Spec was 3 x shelves, with each shelf made of 18mm ply sandwiched together. Each leg was 150mm in height and 45mm wide. Isolation courtesy of an M8 bolt spike inserted in each leg via threaded insert and an aluminium cup inset into the shelf for the spike too locate.
Since I bought my Rega RP6, I’ve had to go back to my old Soundstyle 90s rack due to space restrictions as my (chunky) DIY unit took up a lot of space, and was too high to accommodate the Rega TT self and open the RP6 lid. I clearly didn’t think through how to make the rack easy to adjust for height and fit of different components, or how the system would expand. I intended to rethink my original design, but may now resort to a rack update with a secondhand Quadraspire unit as the DIY effort took so much time and effort, that in the end I figured my time would be better spent elsewhere. Satisfying at the time though. Just make sure you consider how the system may expand.
I’ll look for the photos later to see if I still have them.