Preheat the Traeger wood pellet grill to 300°F (150°C).

Season the beef chuck roast with sea salt and cracked black pepper.

Heat olive oil in the large oven-safe deep pan over medium heat.

Brown the beef chuck roast on all sides for about 5 minutes per side.

Remove the browned beef chuck roast from the pan.

Add onion, rosemary, thyme, and a pinch of sea salt to the pan.

Cook the onion mixture for 3 minutes, stirring frequently.

Add garlic and tomato paste to the pan.

Cook for 1 minute while stirring, then remove the pan from the heat.

Pour red wine into the pan and stir to combine.

Whisk 2 cups of beef stock with all-purpose flour until smooth.

Add the flour-stock mixture and remaining beef stock to the pan.

Return the beef chuck roast and add carrots to the pan.

Cover the pan and cook on the grill for 180 minutes.

Melt butter in a skillet over medium heat.

Brown button mushrooms in the butter for about 5 minutes.

Add the browned button mushrooms and baby potatoes to the pot roast.

Cook uncovered for 90 to 120 minutes until the potatoes are fork-tender.

Shred the beef chuck roast directly in the pan.

Stir in half of the flat-leaf parsley and garnish with the remaining parsley before serving.