You are the most important person in your dog's life - they naturally do not want to be away from you so you need to show them that lots of good things happen when you're not there.
You can always try leaving them with fun toys and games to keep them occupied whilst you're away. Things like this Foobler puzzle feeder are great to keep them busy and not even notice you've nicked off! Get it here on BHG Shop.
First thing is to teach your dog to be comfortable when you're home but not with them. Getting them used to their own space in another room is great. Something like crate training is a good idea (training them to respond to a word like 'kennel', allowing them to enter their box, reinforcing it with a treat, shutting the door as you sit nearby for about 10 minutes until you leave the room) and once they're used to that, start with very short absences.
It's an idea to keep their bed nearby, too, so make sure they've got a comfy one. Try a trampoline one from BHG Shop!
Think about where you'll leave them - how can you make the area comfortable? If outside get them used to their bed.
They definitely like snuggling-up to something familiar, too, so getting them their own towel to bunker down with isn't a bad idea! You can even keep it on-trend by going with a spunky Turkish version, like this one on BHG Shop.
Is the area safe? If the pet is outside, are the fences in good repair or if they're inside, be sure to check things like power cords, wet surfaces, hazardous products left lying around, and so on.
Go shopping for treat dispensing toys and long lasting chews. You may want to check this with your vet as some aren't advised for certain breeds of dog, like deer antlers, for example. You can always have some fun with this yourself, too by being inventive: wrap the treats in paper, put them in boxes, tie them to something steadfast so pup has a challenge. Be creative every day!
A challenge feeder like the Kong classic is a great idea. Load it with some of your pet's favourite treat (peanut butter, chews, etc.), toss and go! They'll be occupied with getting the goodies out of it, they won't even notice you've gone. Get this on BHG Shop.
Take the dog for a walk before you leave or have a game of fetch. This doesn't resolve issues with anxious dogs but makes it more likely that the average dog, especially young dogs, will settle. If you can't commit to an appropriate exercise program consider a dog walker (but check out their credentials first).
Or, just grab a really good lead and hit the pavement! Like this one on BHG.