Had an idea for a round hockey puck for the roland style cutter (After doing those t-shirts last weekend) and very much TRYING to design it. Oh Boy, i have much more respect for those who do things, like design cncs, or parts for cnc, or etc.
This one has really challenged me, but I am getting there. How do you design for tolerances?
Gratuitous shot of my freecad design 
Congrats! Looks pretty good actually.
Is that extruded or revolved?
If you are printing it a good place to start is making holes about 0.2mm bigger, and outer surfaces 0.2mm smaller. From there you can dial in if you need more on your printer.
Lol, not sure extruded\revolved. It is Freecad. Just a series of pads! I am far from a novice even!
At one point i got quite upset, i walked away and came back and suddenly it started to make sense!
That’s pretty good progress, frankly. Grokking CAD workflow can be a really difficult challenge.
Extruded then. 
CAD is hard, freecad is particularly hard. Did you try the Ondsel version, it looks better from a quick glance.
Once you start understanding something even a little bit you start to get better really fast. I think you got over the hump, now you just need to make a couple more things and you will really lock it in. If you are not sure what to make a pair of dice, with all the dots populated…that is a great learning project.
I did mess with ondsel. It is exciting, but i have been messing with freecad, for a while, but never really created anything. Ondsel feels really different! But i think this made things click for me! We will see where it goes.