This seems complicated, it truly is not.
Two pieces of card 4" wide, scored twice on one piece and
three times on the other, the third score is to create the flap.
Adhere the two pieces of card together at the
centre and start to decorate.
You can create pockets for inserting tags,
No deep decoupage would be advisable within
the card or it will not close correctly.
I have embossed metal here and painted with metal paints to
add a special finish. I have also used a cog to hold
my flap shut.
These pictures really do not do this piece justice.