Carlos of GlowSaber wrote a great blog post on how we built an AVR programmer shield:

Building an ATmega328 uploader

As I learned more about Arduino, I realized that it is possible to redesign the GlowSaber around the ATmega328 chip [..] I designed an Arduino Shield that can be used to burn the bootloader and upload programs to an ATmega328 chip.

Here’s a example of an ATmega328 in a custom board:

cvadillo shared the board on OSH Park:

Arduino ISP Breakout shared project