Hi, just joined, if you get a match in material you can mill the hight down a couple of ways. 1 You can router the edges to get the hight you are looking for put the raised section down.
This is the easiest way I can think of, does this make sense to you?
2 have the whole otherwise perfect piece
power plained to the desired thickness, this will give you the most consistent thickness reduction.
3 you can use a hand
power plainer and shave off the down facing side then sand to finish.
Time consuming and you will have varying depths and you should
route the edges that meet/fit into the counter so that you know it’s a constant
depth.
Cheers