First step is to fold your card. You can use a pre-scored card base if you prefer. Let the die show a small amount as shown on the folded side. Tape down if necessary
This is what the folded edge now looks like.
to make your card stand flat score a line on the right hand side as shown. This only need to be 1-2mm. I usually use the first channel that I can score. Cut this small piece off
Now cut a single circle and stick it onto the card base. Voila your little straight line on the fold has gone but...................
Thank you for having a look ...Have fun!
Any questions please ask as a comment and I will try to help