running 328p without crystal ?

Hi, I have designed some small custom boards for collecting data for testing a mechanical product. I based it functions as an arduino nano and i upload to it with an atmel ice. Every thing works great but now i need to add something else and im out of board space in the very tight enclosure.
I actually need to where near the performance offered by the 328p and would like to run it without the crystal to free up some board space, I have read this is possible but cannot find how i will have to compile the code for this to work or is it just fuse settings ? any help would be apreciated

I would recommend using MiniCore - GitHub - MCUdude/MiniCore: Arduino hardware package for ATmega8, ATmega48, ATmega88, ATmega168, ATmega328 and ATmega328PB if using a '328p without a crystal, as it does all this for you and you just have to select "8mhz internal" from a menu and 'burn bootloader'

Described here Gammon Forum : Electronics : Microprocessors : How to make an Arduino-compatible minimal board

Thanks for the help, minicore looks like exactly what i need and looks usefull for alot of things with the extra digital pins.