I wrote a featurescript to create a configurable octagon base (repo name is outdated, sorry!) to work in Onshape!

Here's the Onshape link to the featurescript code: https://cad.onshape.com/documents/526d038b98a28fdcb20dfa41/w/54b6f21c62fce1ec0fb84245/e/e206510d4302d4dd844420e1?renderMode=0&uiState=66dbdd18f3d99d377a8b9104

There is a demo workspace there, with the custom feature being used, and the release V1 notes.

Here are a few pictures on how to use it.

After adding the featurescript as one of your custom features, you can utilize it in your CAD.

All these values can be changed to however you desire, and you are able to download the part created as a result.

You are now able to use the featurescript and download parts!