Recommended · for some experience
Arduino Uno (ATMEGA328P) on a breadboard Tutorial DIY project. Easy guide.
Why people recommend it
A simple tutorial on running a bare ATmega328P on a breadboard and burning its bootloader with an Arduino, though some steps may be dated.
Watch for: One follower still hit programmer-not-responding errors
In their words
Also scrapped everything and tried following this video (and subsequent webpage guide), which makes it look so simple, with a 100nF capacitor in place of the pull-up resistor on the Mega's reset pin.
Carl S on arduino.stackexchange.com, Dec 2020. CC BY-SA.
If you need to conserve power, you could adjust your circuit components in a fashion that will save energy, or if you want to save energy on your Arduino, you could use a breadboard setup(Instructions here and here) or make use of the internal watchdog timer to sleep and wake at certain time intervals.
EngrAbbas on arduino.stackexchange.com, Feb 2018. CC BY-SA.
