My son favours the grey colour scheme. So I made a start with this one.
For the flap I lined a piece of narrow pinstripe with the glittery jumper. I had to sew the lining together from two parts because it wasn't a very big jumper in the first place and after the felting even smaller, of course. The front I put together from the backs of the wide pinstripe trousers so that I could include the little back pocket of the original trousers (top right). The side panels and back are one piece with the stripes rotated by 90 degrees. The piece that determined the size was the flap lining. I didn't use a pattern. I just cut as I went along trying to fit things together. It's a bit frightening but also weirdly liberating. Now I need to find some material to stiffen the trouser fabric. Although originally labelled as needing dry cleaning, the trousers repeatedly resisted being felted in the washing machine. I don't want to make a floppy messenger bag.