Sear the Roast:

Season the beef chuck roast with salt and pepper.
Heat olive oil in a large skillet over medium-high heat and sear the roast on all sides until browned. Transfer to a slow cooker.
Prepare Vegetables:

In the same skillet, sauté the onions and garlic until fragrant. Add carrots and celery, then cook for a few minutes. Transfer to the slow cooker.
Create the Sauce:

In a small bowl, mix beef broth, red wine, tomato paste, thyme, and bay leaf. Pour over the roast and vegetables in the slow cooker.
Cook:

Cover and cook on low for 7-8 hours, or until the roast is tender and falls apart.
Prepare the Mashed Potatoes:

Boil potatoes in salted water until tender, then drain.
Mash the potatoes with butter and milk until smooth and creamy. Season with salt and pepper.
Serve:

Slice the pot roast and serve it with mashed potatoes, topped with the delicious gravy from the slow cooker.

Sear the Roast:

Season the beef chuck roast with salt and pepper.
Heat olive oil in a large skillet over medium-high heat and sear the roast on all sides until browned. Transfer to a slow cooker.
Prepare Vegetables:

In the same skillet, sauté the onions and garlic until fragrant. Add carrots and celery, then cook for a few minutes. Transfer to the slow cooker.
Create the Sauce:

In a small bowl, mix beef broth, red wine, tomato paste, thyme, and bay leaf. Pour over the roast and vegetables in the slow cooker.
Cook:

Cover and cook on low for 7-8 hours, or until the roast is tender and falls apart.
Prepare the Mashed Potatoes:

Boil potatoes in salted water until tender, then drain.
Mash the potatoes with butter and milk until smooth and creamy. Season with salt and pepper.
Serve:

Slice the pot roast and serve it with mashed potatoes, topped with the delicious gravy from the slow cooker.