Slice the beef very thinly against the grain. This works best when it is semi-frozen (but not rock solid). Place the beef in the bottom of a slow cooker.
In a medium bowl or glass measuring up, whisk together the sweeteners, water, tamari, sesame oil, garlic, ginger, and red pepper flakes. Pour over the beef.
Place the lid on the slow cooker and cook on low for 4 to 6 hours, OR high for 2 to 3 hours.
When the beef has finished cooking, spoon some of the broth out of the pot into a bowl. Whisk in the glucomannan powder until combined, then pour the broth back into the pot and stir to coat.
Sprinkle the beef with the chopped green onions and some sesame seeds and serve over cauliflower rice.
