So, here goes. I'll try and explain how to tie a ribbon like this.
1. Cut a piece of ribbon long enough to wrap all the way around your card roughly two times. For the A6 card I used, I cut a piece of ribbon about 70cm long. You need plenty of extra to tie the bow, and then you trim the ends.
2. Take your card and cut two horizontal slits where you want the bow to be. They need to be wide enough to fit the ribbon through, and about 3mm apart.
3. Lay your ribbon over the front of the card where you want it to go then, holding it in place, turn the card over. Wrap the ribbon over the edges of the card and poke the ends through the slits. The back of your card should then look like this:
4. Turn the card back over and adjust the lengths of the ends of the ribbon so they are about equal.
5.Tuck one end under the ribbon running down the front of the card so that you have a ribbon on either side. Adjust the ribbon so that it sits where you want and it is lying flat.
6. Tie a knot around the ribbon running down the front of the card. Just a single knot is fine.
6. Turn the card upside down, so that you have the bottom edge of your card at the top of your work surface (the bows always come out upside down). Make each end of the ribbon into a loop, with the loose ends on the top.
7. Tie a knot with these two loops. I find it works best if you put the left loop over the top of the right one and tuck it round and through. Try to keep the ribbon straight and flat. Pull tight and you will have an upside down bow.
8. Turn the card back round so that it is the right way up. Now you can adjust the bow so that it is the size and shape you want. Pull the ends of the ribbon to make the loops smaller and loosen the knot. Adjust the ribbon, then pull the loops to tighten the knot.
9. Loosen and tighten the bow a couple of times until it is just how you want it. If it's not working, sometimes it's easier to pull it out and tie the bow again.
10. Trim the end of the ribbon to the desired length. Cut either a diagonal or a v shape, to stop the ribbon fraying. There you go, a perfect bow tied round your card and held securely in place.