One of the cutest poses Maisie strikes is the "frog."
I'm not sure when she first started doing this, but my dog walker trained her to do it on command. Now if I say "frog," she will shoot her back legs out behind her, especially if I say it while there's a treat in my hand. But most of the time, she just does it by herself.
When she is hot, it makes sense to me that she'd stretch out like that to have as much skin exposed to the cool floor as possible. It's not limited to indoors though. I've seen her do it at the dog park, and she also enjoys froggin' it out on the dog cot I bought for her last summer. I have a big deck and entertain out there a lot in warmer weather...I wanted Maisie to have a "home base" on which to lounge while my friends and I are grilling or having cocktails. The mesh keeps air circulating so she stays cooler, and she also gets less dirty than when she lays directly on the deck.
That position looks super awkward to me, but I guess it must be comfortable for her!