The base shape is a rounded trapezoid, with a given thickness (tapered side faces).  A circular cutout is made to hold the rubber ring. The parameters in the .py file should be self-explanatory.

To customize: run the  .py file  in a python environment in which the build123d library is availabel (and optional ocp-viewer).

Parameters for the provided stl example:

# --- Plate Dimensions --- thickness = 12 trapezoid_height = 85 long_edge = 101 short_edge = 70 corner_radius = 25 taper_angle = 14 # Degrees # --- Ring Dimensions --- ring_outer_dia = 81 ring_inner_dia = 67 ring_depth = 3 ring_dist = 2 # distance from edge

Python source code was created by Lumo AI (with significant coaching from my side)