Add all stir-fry sauce ingredients to a mason jar, seal with a lid and shake vigorously to combine. Set aside.
Preheat a large, heavy-bottomed skillet, work or braiser over high heat. When pan is hot, add 2-3 tbsp avocado oil followed by carrot, celery, bell pepper, snow peas, chili pepper and the white part of the green onions. Stir-fry 3-4 minutes or until vegetables have slightly softened. Transfer cooked veggies to a bowl and set aside.
Add 1 tbsp avocado oil followed by shrimp and scallops. Cook undisturbed 2-3 minutes or until golden brown. Flip and cook an additional 2-3 minutes. Pour in stir-fry sauce and cook 1-2 minutes or until reduced by half in volume.
Return vegetables to pan and toss everything to coat. Remove from heat, add green parts of the green onion and torn fresh basil. Serve immediately over cauliflower rice.