Randomizer - https://pokehacks.dabomstew.com/randomizer/ - can't tell if you already know about this or if it's just the starting location you want to add to a randomizer

How to make a ROM - - also see desc of Shen's video.

Once you have the ROM, before you hit New Game go to the options menu - Page 2 and change the 'STARTIN' option to Safari.

Hopefully that gives you enough info.