Combine the flour, salt, and pepper. Rub it all over the roast. Melt the shortening in a heavy casserole with a lid or in a Dutch oven. When the shortening is hot, add the roast and brown it to a deep rich color on all sides. Lower the heat and add the onion, thyme, tomato juice, and Tabasco.

Cover and simmer for 3 - 3-1/2 hours, turning once or twice during the cooking. When fork-tender, cool. Remove the fat, slice the meat, and reheat in the degreased sauce, or skim off the fat, reheat, and bring to the table to carve.