Hi Marv, it might have been a good idea to build this centered at the origin, that would then make the world y axis a natural mirroring point.

But here are some potential next steps to make some more progress:

Prepare an inner contour using Construct > Offset:



Draw some center lines:



Use Construct > Offset on those to thicken:



Select all those lines and use Edit > Trim (with Trim mode = keep is more convenient here):



Use boolean difference to cut those away from your base:



If you get stuck on any of these steps please post your current model result and I'll help you with that particular step.

- Michael