Before I went camping on the bike last time, I realised that I want to ride with my spd pedals and shoes. The problem I've seen was what about short trips to grocery, or for a coffee, or just simply to town for a meal or something. I know one option is to have a normal shoes in panniers/rucksack, or double sided pedals. Because I haven't had too much time to purchased them and also walking with spd shoes inside rucksack seems for me like pain in the butt, I've solved the problem in slightly different way.
I've made "platforms" out of 3mm aluminium, so I can attach them to existing spd pedals and ride wearing standard shoes or sandals. They are small and flat after removing from pedals and not taking too much space in the panniers.
All I needed was piece of aluminium, 3mm sheet in that example, couple stainless steel 3mm screws, and spd cleats/bolts. I needed also saw to cut the aluminium sheet to size a file, a piece of sandpaper, and tap 3mm/5mm to make threads in the platforms.
The platforms dimensions are roughly 90x60mm. Aluminium is very easy to cut and file, so no big deal, done in no time.
Next thing I've figured out position of the cleats (basically in the centre), made holes for cleats and threaded them with 5mm tap. Small hint. On the chart (http://www.carbidedepot.com/formulas-tap-metric.htm) you'll see that you'll need to use 4.2mm drill bit for M5 screw, but because the material is so thin is better to use slightly smaller drill bit. I've used 4mm and it was just perfect.
Final step was make small holes for grip pins. They are basically 3mm stainless steel screws. I've used mine with slight countersink but I think better option will be with standard butt head. Hint again. First hole I've threaded, but I realised when I apply small amount of threadlocker on the screw, and force them to screw in, they making perfect thread without using tap. Time saving, and after the thread locker dry out, they are stays in place firmly. The screws from cleats poking just the same height as the other screws so that was fortunate, but if they don't you can cut them to a size.
I've used the platforms couple of times and they're brilliant. I know people touring in standard shoes and platform/bmx pedals but I like the feeling of spd very much so I think that's not for me. The only problem I've found is that you need to learn how to rotate pedals. You'll need to do it in opposite direction than standard road pedals, backwards. First few times might be awkward but then you'll get used to.
The instructable is so simple that I think just set of pictures will be enough.
Keep'em rolling. Cheers.