Just pull the needle up on one (black) side, push the other fibre along the black one and stitch the needle exactly on the same level - forwards.
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Then continue on the same level where you pulled the needle out and stitch a bit back through the black. To make it more comfortable pinned the seams.
And this is how it finished. I wanted to decorate the edges but after ironing I found out that it wasn't necessary. I hope he'll like it :-) I'm afraid it's not the right shape and it won't look nice so I decided to buy him a book for this case ;-)
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