Politely, just dont. If you want to cut work at it, use quartz, use other inexpensive materials, use your machine, make sure things are right. You aren’t going to sit down and facet corundum in your first go its just not compliant and expensive unless its lab. Your very first facet might very well be a big learning experience that takes a lot more stone than you thought, not only to get to your desired angle but then realize how much more is coming off to complete the step. Back up, if you need a stone faceted now look to someone with experience and ask them to show you as they cut your stone.