Heat the coconut oil in a large skillet over medium-high heat. Season the beef with salt and pepper and add to hot skillet. Cook until browned on all sides, about 5-6 minutes; transfer to a slow cooker, reserving any fat in the skillet and return to heat.
To the skillet, add the onion and cook until softened, about 5 minutes. Add the garlic and cook until fragrant, about 30 seconds. Add the coconut milk and curry paste; whisking well. Transfer coconut mixture to the crock pot.
Cook on low for 7-8 hours or on high for 3½ to 3 hours. Add the green beans and stir. Allow to cook for 30 minutes (on low), or until crisp-tender, before serving.
Notes
*check ingredient to ensure Whole30 approved, if desired. Red Boat fish sauce is Whole30 compliant.