1. Prepare Watermelon Glaze: Cut half of a small watermelon from the rind in chunks (about 4 cups of fruit). Cut remaining half of watermelon into wedges for serving; refrigerate until ready to serve. Place in a food mill or juicer and collect the juice. Or place watermelon chunks in blender. Cover; blend until nearly smooth. Pour mixture into a fine mesh sieve over a bowl; discard solid bits. Reserve 1 cup of the juice and drink or freeze the rest.
In small saucepan melt 1, 12-oz. jar apple jelly over low heat, stirring often so it doesn't burn. Stir in 1 cup watermelon juice, the juice and zest of one small lime. Add 2 tsp. red chile flakes, 1 tsp. jalapeño hot sauce, and a pinch of salt. Mix and taste. Adjust seasoning as desired; remove from heat.
Use warm, or let cool and transfer to a clean jar. Glaze will keep, tightly covered, in the refrigerator for up to 2 days.
2. Remove chicken from packaging and pat dry with paper towels. To butterfly, using poultry or kitchen shears cut along each side of backbone to remove it (see "butterflying chicken," below). Turn chicken breast-side up. Open the two sides of the chicken as if you were opening a book, and lay it flat. Break breastbone by firmly applying pressure and pressing down. Tuck wing tips under upper wings.
3. Prepare grill for indirect grilling (see below). Brush chicken with olive oil. Season chicken on both sides with salt and black pepper. Place skin-side down, on center of grill over indirect medium heat.
4. Grill 25 minutes. Turn chicken over. Brush a little of the remaining 2/3 cup glaze on skin. Grill 25 to 30 minutes more, or until juices run clear and an instant-read thermometer inserted in thickest part of thigh registers 180 degrees F, brushing with glaze 2 more times.
5. Remove chicken from grill; brush with the reserved 1/3 cup glaze and let rest 10 minutes. Cut chicken into pieces. Serve with fresh watermelon wedges and sprinkle with herbs. Makes 6 servings.
Butterflying Chicken:Butterflying makes it easy to cook a whole chicken on the grill. Kitchen or poultry shears are the best tool for the job. Make a cut about 1-1/2 inches apart on both sides of the backbone, cutting all the way down, and remove backbone.
Indirect Grilling:This method positions the fire to one side or both ends of grill. Food sits over the unlit part, and the grill is covered so the food cooks from all sides. This is best for thicker cuts that need longer cooking like roasts and ribs.