For this Diamond, you need 2 long lengths of 5mm (3/16") wooden dowel. At least 1.0DL (120cm, 48") each. They are easily cut to the length required with a small hack saw.
Prepare 6 lengths of electrical insulation tape, each
one about 4 times longer than it is wide. Stick them by a corner onto
something handy like a table edge. You can remove them one at a time as
needed.
As mentioned earlier, there's more kite-making on this site than you can poke a stick at :-)
Want to know the most convenient way of using it all?
The Big MBK E-book Bundle is a collection of downloads - printable PDF files which provide step-by-step instructions for many kites large and small...
Every kite in every MBK series.