I don't have pictures of the steps because I started making them months ago and have only just finished them, but I hope it all makes sense, if you have any questions just ask and I apologise for how rubbish my diagrams are. The timing was just a guess because like I said I've been working on them on and off for months.
(Clicking on the diagrams will make them bigger if you can't see the detail.)
Take one of your materials, and spread it out, then take a pair of trousers that already fit well, in the style you want to make, and trace the outline.
Then cut out the pieces leaving a couple of inches of seam allowence.
Repeat steps 1 and 2, for the opposite leg using a different fabric.
Then stitch the sides of each leg together, leaving the croth open. And hem the bottom. Stitch the parts with a brown line in the diagram, leave the poarts with a yellow line.
Turn the legs inside out, and have the backs facing upwards. Stitch the crotch together at the back, but leave it at the front.
Then put in a zip at the front of the crotch and sew up the gap between the zip and the stiches you did in step 5.
Take a strip of material long enough to fit around your waist comfortably, about 6"-8" in width. Then hem the edges of it.
Then hem the top of the trousers.
Then fold the strip of material in half and sew it over the top of the trousers (so you can see about 3" on each side).
Then make two button holes and attach two buttons as fastenings.
All the essentials are now done, and the next few steps are mostly decorative. I then stitched on a few zips randomly.
I then added some belt loops. Which I made by taking small rectangles of fabric, (about 2.5" by about 6") and folding the edges into the middle, and then folding it in half and stitching along the edge. Then folding over the top and bottom and stitching them onto the waistband.
I then added a couple of back pockets.
And this was the finished result.