Schematic taken from this blog post. The only small difference is output header pins drops CTS and RTS pins and replaces with FLASH and RESET signals.
So board input is a standard FTDI 6 pin cable and output is:
pin 1 -> GND
pin 2 -> FLASH (to be connected to GPIO0)
pin 3 -> VCC
pin 4 -> TXD
pin 5 -> RXD
pin 6 -> RESET (to be connected to reset pin)
Project mentioned above exposes FLASH and RESET as a separate 2 pin header.
Schematic preview:
Complete and tested board:
Schematic captured and PCB done using the amazing KiCad!.