I'm making a bed similar in style to the modern bed frame shown by Rockler (https://www.rockler.com/build/bedframe), but king size. The frame is sapele.
With this design, I don't want to need a box spring. There will be lengthwise middle bar with two legs for additional support. Given that, what's recommended for wood/dimensions for breadth-wise support slats to actually hold the mattress?
Also, how wide should the lip on the sides be to hold the slats? I assume 1" is plenty.