It is very easy. Couldn’t tell you percentages though. Combine water and stick of butter in a pan (highest fat content possible), add your weed and bring to the boil. I personally would boil for at least an hour, but would be using more than 25g though. This will decarboxylate as well. Strain the weed through a filter cloth, squeeze as much liquid out as possible. You can save this and redo it, that will let you know if anything was left in there. Allow the pan to cool. The cannabutter will settle on the top and can be spooned off, the water will settle on the bottom and can be thrown away. You can redo the whole process using the cannabutter you just got with fresh weed to further increase the thc content of the butter. There is a saturation point where you can’t get any more thc dissolved in the butter. Good luck trying to get there. No reason it can’t be better than what you buy