Research about ESP8266, how to hardware setup o download firmware into module. This module has some pins that must be in a pre-defined state to be possible the firmware download.

Do a board check All components as soldered well, no short circuits, power supplay components are doing well.

Solder all the board's components, ESP8266 and the peripherals others. Do a board cleanup.

Research about ESP8266, how to hardware setup the module to boot. This module has special needs to boot up, certain pins must be in a pre-definded state.

Do a schematic draw of the module in a simple way using KICAD.
Simple way in this case mean minimalist.

Manufacture the board, this processes consists in, Print the result of KICAD, transfer the design to a fisical board with sensitive film, reveal and etching the board with iron perchloride. Make all drill holes in circuit board, last clean up the circuit board.

The test will be made using a simple firmware to blink a led.

The circuit board design must be do from the schematic generated in KICAD in the issue Schematic.