Season chuck roast with salt, pepper, garlic and onion. Place in a vacuum bag with a sprig of rosemary or thyme on both faces of the chuck roast; vacuum seal.

Place into a preheated water bath set to 131°F and circulate roast 24 hours.

Prepare a charcoal or gas grill and preheat to 450°F to 600°F. Remove roast from bag, pat dry and cover with canola oil.

Grill on first side 90 seconds, rotate 90 degrees and sear 90 more seconds. Repeat grilling technique on second side making sure each side develops a nice char and deep mahogany browning.

Remove from grill, cover with foil and rest 5 minutes before cutting into 1/4-inch slices.