Season the roast on all sides with a few pinches of salt and pepper.

Heat the olive oil in a large skillet over medium-high heat until hot and rippling. Add the roast, and brown on all sides, about 1-2 minutes per side.

Place the onions in the bottom of a 7-or 8-quart slow cooker, toss the smashed garlic on top, and transfer the roast to sit on top of the onions and garlic.

In the same skillet, reduce the heat to medium and add the tomato sauce, scraping up the yummy browned bits from the bottom of the skillet. Add the beef broth, Worcestershire sauce, allspice, thyme, salt and pepper (use less salt and pepper if you used regular beef broth and not low-sodium). Add the bay leaf.

Pour the mixture over the roast. All slow cooker sizes are different but it helps if the meat is mostly covered with liquid (or at least the liquid comes up nearly to the top of the meat).

Nestle the carrots around the roast.

Cover and cook on low 8-9 hours until the meat is very tender.

Transfer the meat, carrots, and onions to a platter and tent with foil.

Remove the bay leaf and pour the drippings/juice from the slow cooker into a large measuring cup (or into a fat separator if you want to pour off excess fat).

For the gravy, melt the butter in a medium pot until sizzling. Stir in the flour and cook for 30 seconds or so. If you have the time, cook for several minutes, stirring constantly, until the mixture turns a golden brown.

Whisking vigorously and constantly (we don't want lumps in our gravy!), gradually add 3 to 4 cups of the pot roast juices, until the desired consistency of gravy is reached.

Continue stirring quickly while the gravy comes to a simmer. Cook, stirring constantly, for 2 to 3 minutes until the gravy has thickened. Season to taste with additional salt and pepper, if needed.

Serve immediately with the pot roast and vegetables (and mashed potatoes, of course!).