Google chooses the method, you comply: video verification is now the workhorse (one continuous phone recording showing your location/signage, business equipment or branded materials, and proof you can act for the business. Unlocking the shop, logging into the business systems). Postcards, phone, and email verification still appear for some categories.
Video tips that prevent re-dos: do it in one take, show street context or signage first, then the proof-of-operations, narrating as you go. Service-area businesses show vehicles, equipment, and branded items instead of a storefront.
After submitting, review commonly takes hours to a few days. If it stalls or rejects, don't create a second profile. Appeal the same one; duplicates convert delays into suspensions.