We bought 9 5/8 yards of sheer fabric, cut it lengthwise and did a french seam to join the two lengths. Then I used my rolled-hem foot on the machine to hem the long raw edge (close to 40 yards of hemming!). We measured it out for the 3 windows and cut & roll-hemmed the short ends.
The fabric runs up into 3 loops across the top over a black rod - spread to cover and a bit of painters tape rolled backwards to hold the slippery fabric at the top of the rod.
J is very pleased with her new window treatments - definitely a grown-up room now!