If you want, skim off the fatty layer on the stew. Heat cooking oil in another pot under medium-high heat. Once hot, fry the pre-boiled oxtail pieces in batches to avoid crowding the pot.

Oxtail tends to be greasy after cooking, so for best results ... and thickens before adding it back to the stew. For more tips on thicking crockpot recipes, visit: How To Thicken Soups, Stews ...