I use a lee 1 oz slug mold for 12 ga.
I use normal 1 0z shot cups as a sabot and normal star crimp
The idea with the star crimp is that you can use the loader you already have and don't need to buy a roll crimp tool.
To be honest I have never had great accuracy with them I have killed a few deer with them.
You must use pure lead with any slug mold.