Set cooker to brown. Lightly brown the roast on all sides in canola oil. Remove roast from cooker and saute onions for about 5 minutes.
Return roast to pot. Combine soy sauce, garlic powder, vinegar, bay leaf and water or beef broth. Pour over pot roast. Set potatoes on top and around roast. Place lid securely on cooker and set to pressure cook on high for 60 minutes, according to your manufacturers instructions.
When pressure cooker beeps and stops. Allow steam to release naturally or press quick release, according to your manufacturers instructions. Use oven mitts when removing pressure cooker lid. Transfer roast to plate and let rest for about 5 minutes. Place potatoes in a bowl and cover with foil.
Meanwhile, if you wish to thicken the gravy, pour drippings into a gravy separator and pour off any fat. Return gravy to cooker and set cooker to brown. Combine 2 tablespoons of flour with 1/4 cup water and pour all at once into drippings. Stir constantly for about 5 to7 minutes until gravy is thickened. Serve along side pot roast and potatoes with a side of green beans sauteed in bacon drippings and garlic slices.