You'll be printing several of the pieces in halves - mostly to optimize the parts for FDM printing.
Sand the facing edges on a flat surface...
Don't blow the plastic particles away. When added to Super Glue, it creates an amazingly strong bond and helps fill gaps.
You'll do this for the main servo wheel...
...and both pulleys.
Clean-up excess glue with an Xacto knife after it dries.
Attach the servo with 10mm screws.
Hot-glue the servo horn onto the pully wheel... make sure it centered!
Attach the pully wheel to the servo.
Rotate the servo carefully and check to make sure that the servo horn has appropriate clearance.
Tap holes, or carefully warm the screw with a hand-torch before driving it into place.
I used two cabinet screws (30mm) to join the outer plate.
Use 8mm screws and printed washers for each pully.
Make sure that the servo wheel and pullys are aligned... to keep the tail a waggin'