I have a very very basic phone laying around and I was just wondering if it is possible to build and install an os on it. I'm aware of the intensified measure required to'build an os' and all, so if possible let's just skip those things in the answers. Thank you. ^_^ BTW the device that I have is a j2me Nokia s40 6th edition
To install an OS in some phones you need special software and hardware. This seems to be the case with Nokia S40 series.
If you really want't to change a phone OS, take a look at supported devices on http://www.cyanogenmod.org/ and give it a try. Another option is the Ubuntu Phone http://www.pcadvisor.co.uk/how-to/linux/how-install-ubuntu-touch-image-3531970/