First of all, welcome to the Thor community! 🙂
As you say, the current PCB is made in 2 layers, but the first prototype was made using only 1 cooper layer. You can find the gerber files and KiCAD files at github if you go backwards in commits. I think that in commit a45186dc852a9880c0d2699d243ae8d5bddf9bb3 you will find that version of the Control PCB.
Hope it helps!