If the recipe calls for it, then yes, it's best to take the time to sear your meat, particularly if you're making beef stew, pork posole, or slow cooker chicken. The dark crust that forms on the meat adds an incredible amount of flavor to your finished dish. If you're using a multicooker, this can be done in the same pot using the sauté function. If you're using a traditional slow cooker, you need to do this in a separate pot, skillet, or Dutch oven. Don't forget to scrape any browned bits from the bottom of the pan into your slow cooker along with the browned meat.