1. Heat oil in medium saucepan over medium high heat until hot. Add onion, garlic and pepper flakes; cook and stir 4 to 5 minutes or until onion is tender. Add chili sauce, water and lemon juice; bring to a boil. Reduce heat and simmer 5 minutes, stirring frequently. Season with salt. Reserve 1/2 cup sauce for basting.
2. Prepare charcoal grill for indirect cooking by igniting an equal number of charcoal briquets on each side of fire grate, leaving open space in the center. When coals are medium, ash-covered (25 to 30 minutes), add 3 to 4 new briquets to each side. Position cooking grid with handles over coals so additional briquets may be added when necessary.
3. Place ribs, meat side up, in large (16-1/8 x 11-3/4 x 2-7/8 inches) foil roasting pan. Pour remaining sauce over ribs; turn ribs to coat. Cover tightly with aluminum foil; place foil pan on cooking grid. Cover with grill lid and grill over medium heat 1 to 1-1/2 hours or until ribs are fork-tender. Carefully remove roasting pan from grill; remove ribs from pan and place, meat side up, on grill rack. Baste ribs with reserved sauce; grill, covered, 10 to 15 minutes, turning and basting once.
Test Kitchen Tips Note: Add 3 to 4 additional briquets to each side of fire grate every 30 minutes or as necessary to maintain proper heat during grilling.