Let's start with the strap. If you haven't got a 1.5" strap kit then you'll need to cut your fabric to suit your triglide and rectangular ring. Take the width of your strap kit and times it by 4. That'll be the width of both of your strap pieces. Then cut one 10" long and another the full width of your fabric.
First of all I like to spray my strap pieces generously with some spray starch. I frequently bemoan the fact that I've starched my phone/posting scales/laptop/husband from some over spray. Hey, hazard of the job right?
Ok, now that you've got your pieces nicely sprayed with starch, fold your strap pieces in half lengthwise, wrong sides together. I'd start with your short piece then move onto your longer piece.
Unfold the pressed piece and fold over 1/4" of raw edge on one of the short sides and press well.
Next take your bottom raw edge up to the centre press line and press into place.
Take your top edge down to meet the centre crease
Fold the whole strap in half along the centre crease and give it a good press.
Stitch along the 2 long sides for the short strap piece and 3 sides of your long strap piece. I tend to sew round all 4 sides because I hate leaving things not quite finished even though it's unnecessary!
Take your short strap piece and thread it through the rectangular ring of your adjustable strap kit.
Fold it in half and stitch near to the ring securing it in place.
Next take your long strap and your triglide buckle. Thread the finished long end of your long strap piece through your triglide and stitch into place.
Laying your buckle face down on the left of you, thread the loose end through the rectangle ring right side up.
Take your loose long strap end and thread it back through your triglide and out the other side.
That's it, strap done!
Come back tomorrow for the flap instructions, phew, today's was a long section!