Just take your card and score your spine maybe 6-7mm left of the central pre-scored fold. You then need to remove a strip the same size from the right hand side of the card, to balance the width of the front and back, and if you want to keep your card square, another strip the same off the whole of the bottom.
So you end up with this...
If you want a thicker spine, just increase your measurements all round. Your card will be smaller, obviously, but if you are making a box for it, you are customising your size anyway so go with what feels right!
This one has a spine of about 2 cm and therefore the card blank once trimmed is about 13x13cm.
Then - get decorating!
For the front of the card I made an aperture with a craft knife and steel ruler, but I didn't want to lose my pretty bird - so I cut round him! A touch of gold at the sides just for bling and a strip of fancy black down the spine to match....
A simple postcard sentiment topper, mounted onto gold and finished off with a handmade rose from another of the stunning papers in the collection. These papers are so lush, I love them!
So you close the cards and you have a little extra feature. all that remains is to make a couple of boxes - don't forget to add a few scraps of paper to match the card inside and you have something very 3D and hopefully very special!