First, using a plier or a socket wrench detach the SNUDDA top from the rotating base. As you’ll only need the top, you can repurpose the ball-bearing base for another project. (A revolving spice tower, perhaps?)
Taking the two MARIUS stool leg frames, fix them to each other according to IKEA instructions.
When that’s done, center the MARIUS leg frame on the underside of the SNUDDA lazy susan. Mark where the legs screws should go on the SNUDDA with a pencil.
Use a drill to drill four holes where the markings are. Be careful to use a drill bit that is smaller than the screws. And to drill about halfway through the SNUDDA. These holes are only meant to help you screw the legs to the table top.
Then get some screws that are about 30% longer than the original MARIUS ones. Attach the legs to the SNUDDA and we’re done.