Quilting question please help?

In theory you could, but in practice it'll be very difficult to double-fold a piece that long accurately. However, assuming you'll be using a rotary cutter and 24"-long ruler, it IS possible to fold a long piece just once and cut it properly - I've done it a number of times.

They tell you to fold twice because it's easier to keep your ruler from slipping on a short cut than on a long one, but if you can learn the trick of safely 'walking' your hand along the ruler to keep it from slipping while cutting, I think it's actually more accurate to cut single-folded fabric.

The two most important things are: make sure the selvege edges are even with no wrinkles anywhere, and make sure your ruler is square to the FOLDED edge of the fabric. If you cut carefully, without the ruler slipping, you'll get nice straight strips without the dreaded "V"s or "W"s.

Good luck, and welcome to the addiction!

1) It's hard to keep the folds accurate and straight, so when you cut you get an actual straight strip instead of one with an angle at each fold.

2) It's difficult to cut more than about 4 thicknesses of fabric for most people, especially when you're a beginner. The more pressure you apply to a rotary cutter, the greater your chances are of cutting yourself.

3) Strips are typically cut on the crossgrain... so if a fabric is 45" wide, it's 27.5 when folded in half, and 13.75" wide when folded in half the second time. Length can be any length you choose, though you'll find it's easier to work with shorter lengths rather than several yards.

Fold enough fabric in half {as shown on the videos} to make no more than four cuts. Leave the remainder unfolded to the side. Straighten the neatened edge and make a maximum of 4 cuts then shake out and refold the fabric. If you try to fold the complete yardage and do all of your cuts without refolding and re-straightening the fabric, you will end up cutting "W"s instead of straight strips.