What you need:
1.Kitchen by Dsixda http://forum.xda-developers.com/showthread.php?t=633246
2./system directory of your custom/stock rom.
3.Root access on phone
Root browser https://play.google.com/store/apps/d...93c2VyZnJlZSJd
Root explorer https://play.google.com/store/apps/d...=search_result
5.Common sense and half an hour (MOST IMPORTANT)
(I presume that you have already installed Cygwin.)
GETTING SYSTEM FILES
1.Install your preferable Root file browser in your phone.
2.Open and look down for system folder in it.
3.Copy the whole folder on your sd card
1.Open your favourite custom rom and copy the system files in there.I personally used creeds v2.5
(Use this method if you want to test it or you are a lazy kid like me!)
SETTING UP ROM
1.Open Cygwin and type "cd kitchen" and press enter
2.Type "./menu" in it. You will see a menu after that.
3.Go to Cygwin>>home>>user>>kitchen>>original_update
4.Make a folder there named as "WORKING_XXXXX" and put the /system files you obtained in it.
5.Go back to Cygwin and press 1.
6.Press enter once again and select the name of your working folder by pressing the number against it.
7.After this it will ask for naming another folder.Do as you want.
8.Now you have a working folder which is going to become your future rom. Select any options from the menu which you would like to have in your rom.(I have not tested all of them so there is a chance that some of them wont work).
BUILDING THE ROM
1.Press 99 to build the working folder.
2.Go for the interactive mode so press 1.
3.Zipalign them by pressing y. A wall of text would come but dont worry
4.Add updater-script. Again a hell lot of text
5.Press y again
6.Sign your rom by pressing y
7.Change the name of your rom by pressing y
8.Press Enter to finish!
9.Go to OUTPUT_ZIP and open the your rom and go in META-INF fodler.Over here you need to put the updater scripts which you want for your rom. I have tested the scripts from Creeds v2.5 and it installs perfectly. (This is not a necessary step because you can also install your rom with the original META-INF script.)
10.Copy the rom to your sdcard
11.Boot in cwm and wipedata+cache and then install your rom.(Have a backup in hand)
12.It should install perfectly cuz it booted properly in my 9/10 tests.
If you want to customise your rom then look below. It should be done before the building the rom.
MORE TO COME: TWEAKS,ICONS,ICS SETTINGS,USEFUL APPS and many other customizations.