Make a mark in the middle of one end of your cardboard - at the 2 1/2" point. From that point measure down 1 inch.
Center your cardboard core at the mark you just made. Trace around it.
You will next need to cut out the circle you just drew. Begin by making two cuts in the shape of a cross in the center of the circle.
Carefully, make 2 more cuts in an X shape. You are essentially making pizza wedge cuts.
Cut around the outside of the circle and remove each of the wedge shaped pieces. When finished your cardboard should look like this.
Next we need to cover the cardboard with duct tape. The only way to cover the inside of a circle is with very small pieces of tape - 1/2" x 2". You will need quite a few of these, so it is best to cut them ahead of time. Lay down two pieces of tape approximately 6 inches long and cut it into 1/2" strips.
Begin laying those pieces on the inside of your circle. Place them on the front and fold onto the back. Be certain to overlap every piece.
Continue with this pattern until the entire inside of the circle is covered.
Cut three pieces of tape to 5" - the width of the cardboard.
Lay one 5" piece half on, half off the top of your cardboard.
Do the same with the two other pieces on the sides of the cardboard next to the hole. When finished you should have a nice frame around the circle. You may have to place some additional small pieces of tape in spots that were not initially covered.
To cover the rest of the cardboard I will be using 12" pieces. Being certain to overlap each piece, lay each piece across the cardboard and fold it onto the back.
Continue with overlapping pieces all the way down the cardboard. Do not cover the very bottom.
All done with Part One. In Part Two we will add pockets and embellishments.