This case is really cool.

Step 1: Ultra Awesome IPhone 4/4S Case! (Step 1-4)

1- You will need to make a rectangle in SolidWorks roughly about 2.36in. in height and 2.5in. in width
2- Do an extrude to 0.45in,
3-Do a cut extrude to a depth of 0.38in.
4-Create posts in the middle of the border of the case that are 0.15in.

Step 2: Ultra Awesome IPhone 4/4S Case! (5-8)

5- Now we need to make the other half of the case; the top half. Make another rectangle with the same dimensions.
6- We must cut holes for the posts in the middle of the border of the case (on the sides) with a depth of 0.151in. The radius is 0.03in.
7- All of the dimensions of the top half need to be the same as the bottom half.
8-Cut the volume control hole as one big rectangle with a height of 1.25in. and a width of 0.27in.

Step 3: Ultra Awesome IPhone 4/4S Case! (Step 9-14)

9- The sleep button hole will be 2.3in in width and 0.4in.
10- The speaker/microphone/adapter hole will be the same dimensions as the sleep button hole.
11- The camera hole will be 0.5in. in width and 0.25in. in height.
12- Fillet the corners on to 0.2in. Fillet the inside corners to 0.2in. also. The edges can be filleted to 0.05in.
13- These fillets will make the case look nice.