Step 1: What You Need
1m of 50mm nylon webbing.
1.5m of 40mm nylon webbing.
(quite easy to adapt to different widths of webbing, but that's what I happened to have around)
Thick black thread, synthetic if possible.
2 x toe clip straps, such as these from Zefal
2 x 4.5mm x 200mm cable ties.
The attached layout file, printed out if possible:
Step 2: Cut Webbing to Shape
Seal all ends by melting with a flame to prevent fraying.
Step 3: Sew Together
Step 4: Sew the Loops
Pin as shown in the picture first and again, do two passes for toughness. Tie off well.
Step 5: Fitting the Toeclips: the Cable Tie
Step 6: Fitting the Toeclips: Threading the Strap
Step 7: Finishing Off
That's you! Take care to set the straps to a suitable diameter such that you can slide your feet in and out easily but can also transfer power from your foot to the pedal.
These toeclips aren't as stiff as others so are much easier to clip into at low speed than when up to a high cadence. Am working on some kind of stiffening improvement for this..