The nose is the key!
Think of it this way: After a long day of work, above we use our eyes and ears to consume content (a movie, music, social media, book reading) that helps decompress and relax.
Just the same, we can help our dogs relax but mainly through their nose, by providing them with puzzles, snuffle mats and exercises for them to snuffle and use their nose in fun way that helps their brain relax. End these exercises with a stuffed Kong for even calmer results!