Description
ATMEGA328P standalone PCB – A nice project for anyone that wants to make a MINIMAL Arduino based MCU board. This board will work for any 28 pin ATMEGA chip like the ATMEGA8 and so.
I have tested this board and it works fine, if you want to program it from the Aduino IDE using a bootloader you must do the folowing. First program a bootloader into the ATMega chip. Find a USB to TTL serial interface that also has a DTR or RTS signal. This is an example of mine.

The standalone board does not have a capacitor in the reset line so this will not work out of the box. You need to cut the DTR wire of the flatcable and put a 103 (10n) capacitor inbetween the lines. Because the Arduine IDE will pull the DTR low for the whole time, and we need only a small reset pulse, this capacitor will take care of the small reset pulse. I glued it onto the flatcable.

Now you can just load a sketch into the Arduino IDE and select the Arduino Uno as board. Then compile and upload to the little standalone board. I tested this and it works fine. Connect a led and resistor to Gnd and pin 13 and you can test the Blink sketch.
This is the project page: https://www.hackster.io/117125/pcb-standalone-arduino-91ccab