I love crates, because I know my dog is safe in there. He loves being in the crate, and he sleeps in his crate at night! The longest I will leave our 17 week old puppy in his crate while we aren't here is 2 to 3 hours, depending on the time of day. If you want to crate your dog it is important to crate train her before you leave her in it.
Another option is a puppy den, a small room, or a space separated out with baby gates. It gives the puppy/dog room to move around which is great, but it can also give her more opportunity to get into trouble. Puppies can destroy baseboards, walls, the door, furniture, their bedding, their toys...they can also "Houdini" their way out of it, so try it out at first in small steps before leaving your dog for a long period of time.
It is not a good idea to leave a puppy or young dog alone for a whole work day. Getting someone to check in and spend time with them is really important for their physical, mental and emotional well being! Even a number of Kongs filled with peanut butter or other foods will not entertain a dog for a full day, but giving her breakfast in the Kong (wet the food, fill it in a Kong and freeze it) in the crate or puppy den as part of training her to love being in the crate or puppy den, that would work very well, especially in food motivated dogs.
Setting up a camera to check in on the puppy while you are at work is also great, however you might want to have a person lined up who can enter your home should there be an issue!