I have seen a few posts on here w/ a DIY on the GRRipper. I built this to fit my current needs. I noticed that the GRRipper models have much more functionality with the blade opening and width adjustments. I will modify as needed but currently this simple designs works great. Of course the main focus was something heavy duty to keep the wood stable and my hand safe. Also, since I have been working w/ cutting thin strips the 1/8 inch end is working great.
Glued a few 1×6’s together, rubber gym floor matting as the base (use a utility knife to graze the surface area for better gripping), and leftover PVC works great as a handle. I received my 1/4 flanged inserts which work great (thanks HuckD). I still have a few knobs left I bought off AMZN and will convert to making my own soon.