For salsa, in a small saucepan stir together honey, cornstarch, and ginger. Stir in chopped peaches or nectarines, celery, orange juice, and lemon juice. Cook and stir until thickened and bubbly. Cook and stir 2 minutes more. Pour into a small bowl. Cover and chill until serving time or up to 24 hours. Spread both sides of ham slice with honey mustard.
Arrange preheated coals around a drip pan in a covered grill. Test for medium heat above the pan. Place ham on grill over pan. Cover and grill for 20 to 24 minutes or until heated through. To serve, cut ham slice into serving-size pieces. Serve with salsa. Garnish with peach or nectarine wedges and celery leaves, if desired. Makes 6 servings.