Maybay jou must make a patroon on paper, i didn't do that,But if you needed it, do so, and cut it out of the paper and outflank that on the fabric, On the wrong side!
choose your fabric, and cut a rectangle with the measures of 31 cm by 37,5 cm.(12,3 X 14,12 inches)
And be sure your fabric is ironed. I had done it later:-(. (It make it easy to tape a smooth fabric!

cut out the fabric two circles of 11,5 cm (4,12 inches)

turn the fabric of the retacgle on the ride side for the taping. I had losted that picture, so i have the fabric make lighter. :-(

began with taping. a truc of myself. I tape with little pieces the fabric on the tableside.
so the taping will be easily and smooth.
The tapes go over the edges and sides of the fabric!

tape the seccond tapestrook half over the first and do that too with the 3e and so with the others .

When all the the fabric is coverd with tape it will show as you can see in the drawing.
click on the drawing, i see that the picture is too large for the frame!

turn the fabric/tape over to the right side. Cut the tape off and following the outline shape of the fabric.

When you have done that on the tape side, its something like this drawing.

The zipper.
Lay the zipper on his place on the fabric. The right side on the right side. See the picture. and stapple the zipper on the fabric.
Attention: do not staple the zipper too near to the teeth.
Because you must allow to fold the cover the teeth slightly.

Turn over the fabric again, the side of the tape is now above and fold the seam down, see the picture.

Tape over the staples, do not tape too near to the teeth, otherwise it could block the slider!!!
Thats for the finishing, and to protect your stuff for damaging on the staples.

something like this.

Fold the fabric and the zipper so that the two ends laying on each other. The right side on the right side (and this is still inside), and the tape outside. and stapple this zipper side on the fabric too.

Tape the both side of the staples down like you have done at the first side of the zipper.

this is not advertisement fot canon:-) My camara couldn't focus, because everything had almost the same collor! So i had to put somthing witht it:-)
On other pictures you can see too materials thats doesn't do matter:-)

when you have done that, it looks something like this.:-)
You must make the zipper open, thats practical for the following staps!

Now you start with the circles. Lay the fabric with the wrong side upside the table.
And start with the duct taping. Likewise the ductaping of the rectangle

cut of the overzised tape. and your done Do the same with the other circle.
when the circle sits not right you can push throug the open zipper the fabric outside so it fits.

Now you have to staple the circle in the gate of tube.
Began with two stapples on the zipper and do it across the circle again with one staple.

stapple the circle on the same way on the other half. See the picture.

stapple the circle where now no stapples are full.

do the same with the other circle.

Now You must finisch the stapples off, by way of taping it off.
See drawing. Start for the zipper point and go over the starting point futher to the point after the zipper. Then it is more strenght.!

Fold the tape over the seam inside. see the picture.

Do the same with the other circle stapples seam too,

Now you almost finished.!!! You can turn the inside out. Do that with care!
I put my etui full to the brim, so I have done extra staples on the downtaped stapple seam of the zipper and i have given it an extra taping off. But that is choice selection of you own!
Good luck and have fun. It seams more diffucult than it is!:-)
I have so much drawing and pictures to make it easyer for you:-) (I hope soo:-))