I think that far and away the easiest kitchen to use is Calkulin's. Download the latest full kitchen with SYS from here:
http://www.myunspace.com/?d=03EA06E01
Start the Calkulin's Diamond Kitchen file once you extract everything. It will open a Command Prompt and give you a list of options. If you just want to cook up your own ROM without adding your own OEM's etc, then just select 1, and then 1 again. It will open up build OS. Then go through and select the items you want and don't want, and just be careful not to select 2 conflicitng Manila files or them files, etc.
Press the play button at the top and wait for Build OS to complete. Once done, close Build OS, and the kitchen will continue to build your ROM for you and just continue through the steps to update your Diamond.
This is a very simplified explanation, but it really is almost that easy.