My idea for adding the vertical slabs in a simple way.

My idea is simple for adding vertical slabs, and it is to add them as a new block; that is, we could call them "flat walls," and they would be the same slabs as always with their same textures, but being vertical and separate from the normal slabs. And well, these "flat walls" will have the 4 normal rotations. I think it's a simple idea. Ah, and they also can't be stacked, meaning you can only have 1 "flat wall"; you can't put a wooden "flat wall" and a stone one, you can only place 1. And here you have about 5 images showing how it would clearly look in the 4 rotations and how it would look on top of a ladder.