Schematics Designing ESP01/12 flash tool is quit straight forward. Before starting, you first need to understand the How-to process of flashing latest firmware into ESP8266 chip.

You can find it here.

This is the best & detailed article i found which help me, How-to upgrade the firmware and also give me an idea to build PCB widget around it.

For 5V version I have added

• LM1117-3.3V LDO
• MOSFET (BS1338) as a logic level translators on RX & TX lines.
• Two Push Buttons
  • RESET
  • FLASH

DOWNLOAD FILES HERE.