Place strips of flanken in a roasting pan in a single layer. Sprinkle with spice rub using one teaspoon per strip. Cover the meat. Place in a cool oven (do not preheat). Turn the heat to 250 degrees. Bake the flanken for about 2 hours. Before you are ready to serve, preheat an outdoor grill or oven broiler. Brush each cooked flanken strip with one mounded tablespoon of barbecue sauce. Grill or broil for 3 minutes. Turn the strips over, brush with more barbecue sauce and broil for another 3 minutes or until hot and crispy.
Place the brown sugar, onion powder, garlic powder, paprika, chili powder, cumin, salt, thyme, crushed red pepper, celery seed and allspice in a bowl and whisk the ingredients to blend them thoroughly.
BOURBON BARBECUE SAUCE:
Heat the vegetable oil in a saucepan over moderate heat. Add the onion and cook for one minute. Add the garlic and Serrano pepper, if used, and cook for another minute, stirring occasionally, until the vegetables have softened. Add the ketchup, brown sugar, bourbon, apple cider vinegar, soy sauce, powdered mustard, chili powder and dried coriander and stir to blend the ingredients thoroughly. Cook over low heat for about 15 minutes or until very thick. Let cool.
Ronnie Fein is a cookbook author, food writer and cooking teacher in Stamford. She is the author of The Modern Kosher Kitchen and Hip Kosher. Visit her food blog, Kitchen Vignettes, at www.ronniefein.com, friend on Facebook at RonnieVailFein, Twitter at @RonnieVFein, Instagram at @RonnieVFein.