ATtiny85 Programmer Board
This is a simple PCB that connects an Arduino Nano with an ATtiny85 to allow for programming of the ATtiny using the Arduino as ISP (in-system programmer). Firstly select the Arduino Nano as your board and upload the "ArduinoISP" sketch from the example sketches of the Arduino IDE. Then you select the ATtiny85 as your board (you need to install it in the IDE by pasting this link in "Additional Boards Manager URLs" under File -> Preferences) and under Tools -> Programmer select "Arduino as ISP". It is recommended to use a DIP8 socket instead of soldering and desoldering the ATtiny85 from the board. Using the USB type C version of the Arduino Nano is recommended.
You may need to downgrade to Arduino IDE version 1.8.18 (or lower) if you encounter the error "-fno-fat-lto-objects are supported only with linker plugin." while uploading to the ATtiny85.
Assembled PCB
The PCB only needs 3 components: the Arduino, the DIP8 base and optionally an LED. I forgot to add a series resistor for the LED so you if you want to use it for validation, you have to write a script that applies a 50% PWM on that pin.
Bare PCB:
BOM
=> Arduino Nano
=> DIP8 base
=> 5mm LED*
*optional