Heat the oven to 350 degrees.
Season the pork chops generously with salt and pepper. Set aside.
Place the flour in a shallow plate and season with onion powder, paprika and cayenne. Season with salt and pepper and stir with a fork or whisk to combine. Set aside.
Heat the oil in a large skillet over medium-high heat. Meanwhile, one piece at a time, add the seasoned pork chops to the seasoned flour and turn to lightly coat.
Once all chops are coated, shake off the excess flour, reserving it for use in the gravy. Working one chop at time, transfer the coated chops directly to the heated pan and sear until golden brown, 1 to 2 minutes per side. Set chops aside on a plate.
Add the onions to the skillet and decrease the heat to medium. Season with salt and pepper. Cook, stirring occasionally, until the onions are golden brown, 5 to 7 minutes. Add garlic and cook until fragrant, 45 to 60 seconds.
Add the remaining flour-spice mixture to the onions and stir to coat and combine. Add the chicken stock while stirring the onion and flour mixture. Increase the heat to medium-high. Bring the mixture to a boil, then decrease the heat to low and simmer until the mixture thickens into a gravy, 1-2 minutes.
Add to the skillet the reserved pork chops with any accumulated juices, thyme sprigs, and the bay leaf. Nestle the chops into the onions and turn to coat all sides in the gravy.
Transfer the skillet to the oven, uncovered, and cook until the internal temperature of the pork chops reaches 145 degrees, 8 to 10 minutes.
If the gravy seems too thick, remove the pork chops to a serving plate and add additional chicken stock, a little at a time. The sauce should be thick enough to coat a spoon.
Taste and adjust for seasoning with salt and pepper. Serve immediately.