It's not my favorite way to cook it, but this is helpful if you need to leave it to cook and leave the house. First, sear beef chuck on the stovetop first. Then transfer beef, along with all the other ingredients, into the slow cooker and cook on high for 4-5 hours or low for 7-8 hours. Thicken by adding cornstarch and water mixture, then cover, and let it cook on high for another 30 minutes.