I decided to try CalyxOS on my new Pixel Tablet. Bad move. Do not like. Want to switch to GrapheneOS.... But... How do I do it safely without bricking the device? When I was installing Calyx it said that if I had a different non stock os installed to install the stock is first and then do the graphene one. Is the same true for GrapheneOS? Do I need to somehow switch back to Pixel OS first?

You can flash directly from CalyxOS. You don't need to flash stock PixelOS first.

You don't need to worry about bricking your device whilst flashing GrapheneOS, especially if you use the web installer.

You can follow the instructions on the website like normal, and let us know if you need any help: https://grapheneos.org/install/