The circuit I'm using in these is just an electrical current control. There's no flash patterns or anything. The blinkers will use an electronic flasher relay replacement for the stock one since with the low power draw they'd just be on, not blink otherwise. The brake light will use my foot/hand as the flasher.
I'm not convinced that the DIY method will necessarily be any cheaper than buying a pre-made unit. However, I'll know that I've used good components, and that the assembly is good. Plus it's fun to do.