Heat olive oil in a skillet over medium heat. Stir in onion and cook until softened, about 3 minutes. Stir in garlic and cook 2 more minutes until softened.
Place venison roast into a slow cooker, and sprinkle with onion mixture. Stir together ketchup, Worcestershire sauce, soy sauce, chile-garlic sauce, water, salt, and pepper. Pour over the venison.
Cover and cook on Low until tender and no longer pink, 4 to 5 hours.
