here a tutorial to do a cloth diaper "all in one" with a funny fabric (fashion style!)
I have picked the materials for the diaper on a French site named couche-nature.fr. i took this for the impermeable part and this for the size that is "in touch" with the skin, it's micropile (I know, it is not as natural as bamboo or hemp but I like it because it leaves the baby skin dry).
for the external decorative fabric, you can obviously use what you prefere. and for the inside absorbent part, I have sewn some double rectangles in hemp (I bought hemp here).
1) I have started by doing the pattern from a diaper I had already just to have an idea about forms and measures.
2) cut the 3 fabrics in the form that you have drawn.
3) cut the upper micropile side (if you use the microplile), it's from there that you will insert the stuffing. the micropile do not fraye but I have stitched two little points to avoid that the opening opens too much.
4) now assemble the impermeable part and the colored fabric (i didn't put pins to don't make holes in the impermeable fabric, i fixed them with TAPE)
then, with a cloth pen I marked the points where will be the buttons (or the strap). position the fabrics wrong sides together.
I have added a small rectangle of micropile before putting the buttons to consolidate the fabrics.
5) you should now have these two pieces: the fabric of micropile already "shaped" plus the impermeable fabric and that decorative one kept together from the buttons (or from the strap)
(in this pics i didn't finished putting buttons. it take too much long, i hate this part!)
6) assemble the two pieces (that are actually 3, if you follow) right sides together. (oh yes, also the micropile has a side!), pin in place (put the pins in a more external position in comparison to where the seams will be for avoiding to have a riddled impermeable part!) and sew the whole perimeter.
nb: you don't have to leave openings because you will turn the diaper (inside out, at the end) from the opening of the micropile (smart^^)
7) after having sewn the perimeter, you can add the elastic. the elastic is sewn with a zigzag point holding it taut. and it must be put in the narrowest part (where will be legs) and also in the upper part (where will be lower back).
did I explained my slef? :S
8) turn it inside out
9) now you can add closing buttons (or strap)