How do I get a 4-way linear movement with a slide?

Definitely should have the floor mesh isolated and put it in a different collision channel so you can then specify not to make contact with it ever. Or even better, since the floor is just decoration, if you never need it to collide with anything you could just remove it’s collision altogether. That said you would still have to edit the box so the floor is not a part of the walls and internal bricks.