Welcome to the SeeMeCNC Community

I downloaded a knob with a gear perimeter to continue to learn. I downloaded it from Thingiverse.

Right: I stopped the job. Clearly it was wrong.
Center: I stopped the job after futzing with temps.
Left: I went to Slicer Printer Settings, Print Settings, and Extruder Settings.

Print Settings:
Layer Height: .4
First Layer: .35
Perimeters: 3
Horizontal Shells: 4 & 4
Infill: .9 (from 1!)
Fill Pattern: Honeycomb
Top/bottom fill: Rectilinear (seems to be decent)
Infill Every: 1 Layer

Extrusion:
Diameter: 1.75
Extrusion Multiplier: 1
Temps: 240, 240, 70, 70

Printer Size: Left it alone since it's a small print.

The left image layer heights appear to be close. I might try shaving down the layer height a bit.
More or less the print had flashing or feet at the bottom. Is this because of the Perimeters setting?
The hole for the knob was filled in. Perimeters?
The top wasn't 100% filled.

Any tweaks to get a perfect or close to perfect print would be appreciated!

Printing a gear or anything with small features, I usually will set the perimeters to a minimum of 1. For there slic3er will use more if it knows it has the room. Your first layer height/z=0 setting/first layer settings in the advanced section of slic3r determine how squashed the first layer is. It has to be expanded somewhat to achieve good adhesion. If you want to get rid of that I would look at a raft instead.

Thanks!