Detail in the top

I want to run a detail of walnut down the middle of the two juniper boards, something to unite the base wood and add a subtle yet challenging detail to the top.

So the gap is a little wider at one end than the other, sort of like a small river, as the sides get closed in the water twists and turns a little, I've bunched the pieces of end grain at that end also, making them a little smaller and tighter.