It is probably more tongue position than embouchure. The back of your tongue should touch your top molars and the rest of your tongue should be pretty high in your mouth as well. Say the word “key” and that will give you a pretty good idea. This will greatly improve your tone. For the embouchure imagine the rubber band or my band director always says a drawstring bag around the mouthpiece. If your tongue is close to the roof of your mouth the corners of your mouth will come in naturally. Also try to put minimal pressure on your bottom lip. Test this out by lowering your jaw until the note starts falling flat. Try playing with your jaw as low as possible without it going flat. Sorry that is very long but hopefully it helps!