This is a drop in car dock. I had a similar one for my google pixel 2, but needed a wider one for the larger Pixel 4a5G. The only modification was I made holes in the base for the speakers (also uses less material) and its wider. I am using a Spigen thin case, with the phone its about 78mm wide.

The backing plate is designed to use captive nuts and mount to a RAM mount diamond base plate. I use this one to attach to the pillars in the center console of my Chevy Volt. https://www.rammount.com/part/RAP-SB-187U. There are other RAM mounts available that use the diamond and its a strong connection for the cradle.

If you are interested in this, this is all parameterized in Fusion 360 so I can create an STL for different width of phone, different size holes for USB, etc.

I printed this using black hatchbox ABS on a pretty stock Anet A8. ABS is nice and durable and more heat resistant than PLA which is better for the use it will see.