some builders' "hot tack" with the cutting tool,... take a fine edge soldering iron tool tip and make it more needle like still with a jeweler's file or emery board. Lightly tack every few inches to weld the fabric strips in place. The best kept secret to this technique is to sew thru the hot tack holes and hide 'em! You can pick-up a hot tackers work and see their holes when backlit usually, 'cause hiding 'em entirely is tough.
SprayMount light-tack adhesive from several feet about of the work and let it drift down onto the fabric is another technique to prevent that material from slipping around. Go light and see if it's enough to hold, .....you don't want to clean-up with bEnzene if not required.
some use blue painter's tape to hold pieces in place, slowly removing it just before entering the jaws of the sewing machine.
Some folks waste fabric with the Randy Tom Method, using full pieces of every color, sew the parameter thru all layers and cut away color afterwards from both sides until you arrive at the desired layer.
some builders used a spray bottle with just water in it, wet capillary action holds the pieces in place and needless to say, clean-up is a breeze, no foul chemicals to inhale either
Go to a workshop on kite building and steal everyone's best ideas, see which way works best for you, practice before you waste expensive materials. The amount of labor is not different if you cheap-out of the fabric choices available.