Field-based classic grounded theory applies Barney Glaser's original (Glaserian) grounded theory method within naturalistic, in-situ settings — combining sustained field immersion with the classic GT emphasis on emergence, theoretical sensitivity, and the constant comparative method. The researcher enters the social scene without a predetermined framework, collects data through observation and naturalistic interviews, and allows a substantive theory to surface inductively from the field rather than imposing conceptual structure in advance.