why dont u use a quilt ..i have 2 greys and a yorkie and thats what they use to sleep on..when the covers get grubby i just wash them..tonnes cheaper than buying/making a fancy dog bed xx

I have a yellow Lab as well.
When your dog is laying down on her side and she is streched out measure how long she is ...you can even mesure her when she's standing measure from the tip of her nose to her butt. This way when you make the bed she'll have enough room to curl up or stretch out.

I would measure the dog, and add about 6 inches in length to that. For example, if your dog is 36" long, then make the bed 42". As for width, since she is a big dog, I would say about 30-36 inches wide. If you are still unsure, you can always go to a pet store and get ideas off of their beds there.

Personally, I just fold a queen size comforter in 4 and my dog loves that! (And its super easy to wash).