The unpopulated PCB component side up.
Solder in the IC socket, ensure the cut-out in the IC holder matches the cut-out on the ident on the PCB
insert the two buttons and solder in place
Insert and solder in the switch and the three capacitors
Insert and solder the 5 resistors and the regulator.
add the LED the flat on the side of the LED needs to go to the square pad on the PCB
Solder in the two capacitors, match the white stripe on the capacitors for the white D on the PCB ident
Solder in the transistor
Finally flip the board over and solder the slotted opto on to the reverse of the board.