I’ve made legs for one of the baseboards. The legs are 44mm x 44 mm timber and the bracing is 43 x 20 mm. They are joined together with 40mm screws.
Next I added some 8mm bolts and wing nuts. (I brought these from Bolt World on ebay. I couldn’t resist a shop with a name like that!)
I added a couple of horizontal pieces of 43 x 20 mm to create a frame.
One of the baseboards can be placed on top.
Yeah, it works!
Now I need to repeat the process for the other baseboard.