I recently bought a new smartphone, the brand and model is fairly uncommon(Archos 50c Neon).
I was looking for a flexible(rubber/silicone) cover similar to the one I had for my previous phone but these covers are avaiable in almost every store only for the most popular models of smartphones(usually some versions of iPhone, various Samsung, and more rarely LG, Nokia, HTC).
Being unable to find a dedicated rubber cover and finding universal wallet covers not suited for my needs I decided to try make myself a flexible cover for my smartphone. I opted for clear silicone because it's easily avaiable and because my phone was packed with 2 exchangeable backs(one black and one in a nice fluo yellow).
Step 1: Materials
Plywood(I had a leftover)
Silicone (a silicone cartridge for 2.8€, about 3$)
Plastic wrap(the roll used in the kitchen)
Step 2: Internal Mold
I used a piece of plywood to reproduce the smartphone size and shape.
I selected a plywood similar in thickness to the smartphone, I cut a rectangle with the same dimensions and then I rounded corners and vertices using file and sandpaper.
I also traced with a red felt pen important references as the display area, phone jack, microUSB port, microphone, camera lenses, speakers etc.
Step 3: Wrap the Mold
In order to avoid the silicone to stick to the mold forever I decided to wrap the mold with plastic wrap. I did twice because I also added the detail of the bump near the camera lens.
I decided to be careful and avoid wrinkles on the back side and be less careful about the display area that will be removed later.
I also used a little of water+soap to help avoid the silicone to stick too much to the mold.
Step 4: Add Silicone
Now you have to cover the mold with silicone, and this could be done in different ways but I tell what I did
I put a generous ammount of silicone on the back side of the mold, then I used anothe piece of plastic wrap.
I layed this plastic film on the table and put the mold back-down on this plastic wrap, then I applied pressure on the mold with my hand, this pressed the silicone between 2 flat surfaces obtaining a nice and uniform back side. At the same time the excess silicone exceeded the mold sides. Probably it will exit only on the sides and not on the corners, so If needed you have to add more silicone at corners.
Ad this point I used the plastic film( basically wrapping the mold+silicone) to obtain the cover sides and used fingers pressure to model the result.
Then let it dry.
Step 5: Remove the Mold
Unwrap the external plastic film
Use a cutter to cut out the desplay area.
Then extract the plywood mold through the display area.
Remove any remaining plastic wrap piece from the silicone cover.
Check it's actually dry and not still sticky before placing it on the actual phone
Step 6: Cut Out Holes
Put the cover on the phone and check the required holes position matching with the phone
then put the cover again on the plywood and using the cutter cut out the holes.
Step 7: Final Result
Here you can see the final result.