The Base design is from this "Amazon Echo Show 8 stand by waschbaerbauch75 on Thingiverse:" - https://www.thingiverse.com/thing:4182781

Summary:
I found this popular Echo 8 Stand design and made a few simplifying "adjustments."

The design includes four pieces:
Stand - print flat with tree support. Infill of 25% works fine - more if you like.
Mount - print flat with tree support. Infill of 100% for strength.
Base - print flat, curves facing up without support. Infill of 25% works fine.
Centering Bar - there is a slight bevel, print wide part flat on plate without support
Use a couple drops of glue to lock the mount to the base and the bar to the opposite side of the base. The use of a brim helps to ensure the pieces stay flat and in place.

To assemble you need a M4x20 screw, a M4 screw nut and a fitting washer. Doouble up the magnets for a stronger grab to the Echo. I used these neodym magnets (10mm x 2mm) from Amazon: https://amzn.to/3abLsWL

Thanks to waschbaerbauch75 for his base model - much appreciated.