Really well done !!!
I've tried this before too and it takes a lot of patience to actually draw around and move the pieces that you want to take out of the puzzle.
I don't know how this would work as a real puzzle - that grassy area looks like it would be impossible! But as an overall image this has all come together very nicely.
The original photo of the dog is lovely - strong colours and an appealing pose, and I like the wooden floor / table that you've used as a canvas to place your puzzle on.
I think you could maybe do with a little more tweaking on combining the two elements though. The angle of the puzzle vs the angle of the table aren't
quite gelling for me as it is. It gives the appearance that the table was shot from a higher angle, so I'd suggest either reducing the amount of perspective distortion on the puzzle layer to make it more "square", or reshooting the table layer from a lower angle.
A very subtle drop shadow added to the puzzle and the individual pieces would also make them look more "there" (if that makes sense!)
ahhh the ones at the top you mean?
Ahhh - I noticed that too.
TBH it's not something that instantly jumps out at you as being wrong, and I'd be tempted to leave that as it is, rather than lose the square edge to the puzzle. It's only on really close inspection that you notice those tiny tabs on the outside.