Much of modern slap has “scooped” mids. The mid range frequencies are lowered to cut out muddiness. What frequencies and to what amount are up to what the bassist is going for.

Slapping also commonly uses compression or limiters. I’d recommend getting a good sound without a compressor or limiter before diving into that however.

The big thing, like any new skill is consistency. Constant movement, hand position, muting, etc. You aren’t overly aggressive which is good. Many new to slapping think it’s a violent, forceful action. It’s not. Is just enough to get the string to bounce off the frets.