Add pork tenderloin to a 6-quart slow cooker.
Combine bbq sauce, mustard, chili powder, and kosher salt (and any other spices you'd like, see notes).
Pour bbq sauce mixture over the pork tenderloin and add the lid to the slow cooker.
Cook on high for 2- 2 ½ hours or low for 4 hours, until the pork tenderloin reaches 145°F.
Remove from the slow cooker and rest 10 minutes. Slice and serve with sauce.
