There are a number of Walabot holders/cases that assist in keeping the phone and the Walabot together while in use, but at the time of this design, they're all phone-specific. There's also one with a center guide, but no phone attachment (https://www.thingiverse.com/thing:6159576). This design aims to make the design more phone-agnostic, as well as provide center guides for the holder. Both the phone attachment and center guides are modular/optional.

There's a plain/regular version of the center guide, and a USB version. The USB version has a cutout to allow for plugging in the Walabot while in the case. This cutout was placed based on my measurements of my Walabot DIY 2. I do not know if the placement will work on other versions of the Walabot devices.

I'm sure there's going to be phones that don't work well with this, but the goal is to get it to work with the majority of phones. The back comes up about 1/3 of the height of the phone (plus a little more for the top of the circular portion) to allow for devices with protruding cameras near the top. The inside edges have a slight rounding to them with indentations that run half way down on both sides to allow for power, volume, etc. buttons. There's also a cutout in the center of the bottom to allow for USB plugs to connect to the phone while in the case.

The STL file I've included here for the phone holder is specific to my phone and case. See the "How I Designed This" section for the link to the original model so you can make you own phone holder (unfortunately OnShape doesn't export SCAD files for me to use the "Customizer" option in Thingiverse).