How do mods balance a game of Werewolves?

Hosts/Mods usually access a separate page to create their setup, with role cards provided. Each role card holds a specific score (e.g. Seer is at 9 points, GrandVizier at 8 points, etc.) which then is tallied with the other scores to generate a predicted percentage for each faction that's added into the setup.

At this point, each host/mod builds their setup in their own way. I'll answer by sharing how I build my setups, which should give you some basic insight. Other hosts/mods are encouraged to add their input as well.

When I create my setups, I usually start with a particular theme (e.g. Subfaction war, GY-heavy intel, etc.). Once I've added the roles I want in there, I start tweaking the setup to make sure the balance is slightly more favoured to the village (e.g. Village:Wolf = 55:45). I'll not always achieve that exact ratio, but I'll try to get as close as I possibly can. If the setup has more factions (e.g. coven), then village gets the highest chance, and a bit more leverage to coven over wolves. There will be some setups where I don't try to get the exact ratio down, and the setup is made just to have some light-hearted fun.