Mix garlic and ¼ cup oil in a large bowl. Add squid and toss to coat. Heat a large heavy skillet, preferably cast iron, over high 5 minutes (you want the pan scorching hot). Working in batches to avoid overcrowding, cook squid, turning halfway through, until lightly charred and cooked through, about 3 minutes total for bodies and 40 seconds total for tentacles. Transfer to a cutting board. Let cool slightly, then slice bodies into ½”-thick rings.