Depending on which MCU Devlopment board you have chosen, you will need to figure out a way to mount this to the chassis. I have seen everything from cardboard, to aluminum, to wood.
Below is a template complete with CAD drawings to mount the Qorivva TRK-MPC5604B board and the Motor Board onto the chassis.
We use plexiglass for ours, but any other millable material is appropriate. The large hole in the middle is for cables from the servo. We attach the board to the car using the
plastic standoffs (you will need them 55 mm long, so in our case, we used the combination of 40 + 15 mm) - see an example (SOS code 10260).
To attach both the processor and interface boards the simillar 5mm plastic standoffs were used.