Combine brown sugar, mayonaise and chili sauce until reasonably smooth. Add garlic and liquid smoke. Set aside.
2Cover bottom of crockpot with rib meat pieces. Cut 1/2 of onion into petal size pieces and spread on top of meat. Dust with seasoning salt to flavor. Pour 1/2 of sauce over all, then repeat for a second layer. Set crockpot on low and cook 7 to 8 hours.
3At 6 hours skim off fat. Desolve cornstarch in water and add to pot. Stir carefully. I find that this is frequently done in 7 hours so be sure to check for doneness at that time.