Cases like these can be bought at webshops, some examples are :
- http://www.grovemade.com/product/iphone-5-case/#plain-bamboo-iphone-5-case (79$)
- https://www.miniot.com/webshop/?portlet=miniot&page=iwood5&state=maximized (79$)
Just as much as the iPhone is a precision device, manufacturing this case will require precision.
Apart from that, with basic tools and very little materials, you can build a really impressive protection for your phone.
Step 1: Warning
an iPhone is a delicate thing, and as such does not really belong in your woodworking shop : It doesn't like dust.
Also when working with glue, make sure everything is dry and clean before touching the phone
Finally, when you make this case, be very careful towards scratching your phone's display
Having said this, you will need to measure, try, proof, etc. from time to time with the real phone. The wooden case needs to be very precise in order to function well, and this precision can only be achieved through regular testing and proofing while building it
If you feel unsure, you can make an iPhone dummy (a wooden piece with the same dimensions) and then proceed with this dummy.