For a first try, you did a great job on your satin stitch applique! It does take a lot of practice, and using stabilizer. I used to use typing paper, but now use examining table paper....just the right weight...heavier than tissue paper, but tears away easily. Another thing is to loosen your top tension a bit, that will bring more of the thread to the back of your piece and gives a smoother stitch. I have a Bernina, and my bobbin case has a hole in the finger of it which I put my thread through, that sort of tightens the bobbin thread a bit without having to touch the bobbin tension. Have fun! Usually once you are done if you press with some steam, the block will flatten out.