Organic or not, I start my auto's off in a six inch pot, and when it needs up potting, move it to its final pot, job done.

I germinate in Jiffy pellets, then transfer to pre-moistened 5 gal container day after sprout. Top third of medium is FF Light Warrior and perlite, giving taproot time to acclimate (7-10 days) before hitting the "hotter" dry granular fertilizer amended, bottom two thirds of medium. Then it's water only for 7 weeks. I'm totally inept at transplanting, but I know how to water and this works for me.
Organic soil auto grower.