Trim fat off pork chops and season generously with seasoning salt.

Heat oil in a large skillet over medium heat. Add pork chops and cook until browned, 3 to 4 minutes per side. Transfer pork chops to a plate.

Pour chicken broth into the skillet and bring to a boil while scraping the browned bits of food off the bottom of the pan with a wooden spoon. Add mushrooms, onion, and butter; simmer for 5 minutes. Transfer 2 tablespoons of sauce to a small bowl.

Add flour to the sauce in the bowl and mix with a fork until no lumps remain. Pour slurry back into the skillet and stir until combined with the sauce.

Return pork chops to the skillet. Cover and simmer for 15 minutes. Remove lid and continue cooking until gravy has reached desired thickness and pork chops are no longer pink in the center. An instant-read thermometer inserted into the center should read 145 degrees F (63 degrees C). For a thicker gravy, mix in more flour.