Combine all sauce ingredients into a dish and whisk together until sugar is mostly dissolved.
In a large bag marinate the steak with the sauce mixture overnight or at least for 3 hours in the fridge.
When ready add the steak and remaining marinade in bag into your slow cooker with 1/2 c of water.
Cook on low for 8 hours, then remove to a cutting board and shred meat. Can put back into crockpot with remaining sauce on warm if serving for a party or serve immediately in small tortillas to make Korean beef tacos.