How to attach a "live edge" slab to the top of my bar

So I have completed the Chinquapin breakfast bar portion but I want to attach a shelf. For support I left the two front legs of the bar a bit long. I can then seat the live edge slab of madrone (roughly 2” thick) on top of the legs. My confusion is how to attach it. I have two corbels out of madrone that I plan to screw into the legs and the underside of the madrone slab for support. But I’m thinking I need more to stabilize the slab. So I’m wondering….do I cut a couple blind mortises on the underside of the slab that will accept the top of the legs(about 2”x4” in size).... and if I do that do I need to make it loose to allow for expansion? The direction of grain in the slab(along the length) is perpendicular to the direction of the wood movement in the leg. Is the leg (movement will be along the 4” side) small enough that I don’t need to worry? Can I glue this mortise? Or should I just drill through the top of the slab into the end grain of the leg (yech), lag screw it and plug the hole?

I added some pics below that hopefully show what I intend (the slab is just sitting on the legs right now and the corbel is taped- all for the camera….).
If I have not made myself clear- please ask and I will try to clarify.

Here is the slab resting on the legs for a picture.

close up of the meeting of the corbel, slab and leg looking from underneath.

same as previous from a more overhead perspective.

view of just the corbel without slab on top. As you can probably tell I am still working on the corbel!

Here is one corner of the bar showing the extension of the leg that one end of the slab will sit on.

Any ideas/suggestions would be greatly appreciated. I’m a little stumped here. Thanks in advance people!

-- The only gift is a portion of thyself. -Ralph Waldo Emerson, writer and philosopher (1803-1882)