I have only connected TX,RX and GND to the pl2303 board.
I used the links provided in this link for the esp flasher tool and the firmware binary file:
www.xess.com/blog/esp8266-reflash/
I had the following setup for flashing my ESP8266-ESP12 test board:
ESP RX to Pl2303-TX
ESP TX to Pl2303-RX
ESP GND to Pl2303 GND
powered my ESP8266, with 3 AA Batteries
Supplied a separate line 3.3V and GND to a breadboard from Arduino connected to my laptops usb port.
Connected GPIO2 and CH_PD to 3.3V
GPIO15 to GND
Placed the jumper(GPIO 0 to GND)
Hope this helps.