I wouldn't use the Low setting to rise dough - most crockpot's set on low would start baking the dough. You can however, try doing that on the warm setting. Some crockpot places also will sell you inserts for baking, for steaming puddings, for rising dough and so on. You can accomplish the same thing by setting the crockpot on warm, filling the stoneware liner with an inch or so of water and then placing the dough in a stoneware bowl inside the water bath so the dough isn't coming into direct contact with the warmest part of the sides of the stoneware liner (which rest against the metal heating element).

Cooking with a slow cooker is by its very nature imprecise. You set it on low and walk away for 8 hours. Or, you set it on high for a couple hours and then switch to low and walk away for 6 hours. That kinda thing.

There are some helpful websotes that explain the basics. I'll look for them but you can find them just as fast by googling on the temrms Slow cooker basics or Crockpot cooking introduction