First cut off a 1/2 yard straight piece of fabric. Unfold it so you have your selvedge edges on either end of the long strip. Fold one corner till it is even with the bottom of your rectangle, you will cut here on the fold. Now you are left with this:
Next take your triangle selvedge edge and place with the selvedge edge on the other side, the shape will look like this:
Sew these right sides together and press open your seams. Next you will draw lines parallel to the slanted edges of your fabric on the wrong side. Decide how thick you need your strips of bias to be. I have thick rope so I used 2 inch lines. The long straight top and bottom will be a seam so I marked off 1/4 inch seam allowances, this will help you match up your lines later.
Next you will need to bring your long edges together starting with the first parallel line you drew (on your long edge) meeting up with the second parallel line you drew at the edge on the bottom. IF THEY ARE NOT STAGGERED THEN YOU WILL JUST BE CUTTING OUT USELESS RINGS OF FABRIC. Ask me how I know this? LOL
So you see you have a twisted mobious looking tube here. It will have tails of fabric on either end because we staggered the lines. It looks all screwed up I know but just trust me and go sew your seam. Press it open using a pressing sleeve.
Now comes the moment of truth! Take your scissors and start at one end cutting through a single layer of fabric round and round through your yards of bias strips.
Ta da you did it!
Now you can make bias tape, or piping, trim etc.