I would suggest printing this upright. You can print it in less hardy materials like PLA as it won't sustain much of a beating. Make sure to print with plenty of perimeters and top and bottom layers. I think mine were 2.4mm thick!

You will need to print the thwack hammer with the hammerhead pointing downward and pause / cancel the print just before it reaches the handle. Check your slicer for instructions on how to schedule a pause in the G-code. 

I used Nylon for the hammer section and PLA for the handle.

Goodest of luck.

https://www.printables.com/model/46099-thwack