I’m planning to build a rather small table, 28 x 50 x 17 (b x l x h). The extra is there’s a bottom shelf between the legs at about 2,5 inch from the floor. the legs are just inside the corners of the top. my question is how to contruct this extra shelf (solid oak) between the four legs without pushing them apart when the wood expands or leaving a gap. hope you can come up with some hints.