Learning how to build custom audiences without detailed targeting enables brands to retain first-party data advantages while respecting platform constraints that limit third-party demographic filters. Traditional approaches relied heavily on interest stacking, job titles, and lifestyle segments, but Meta's deprecation of many of these options forces marketers to architect audiences around website visitor data, customer email lists, and behavioral pixel events instead. The resource walks through lookalike audience construction from high-value customer segments, custom audience layering strategies that work within Meta's simplified interface, and methods for testing audience quality without reverting to legacy targeting rules. E-commerce stores and lead-generation businesses find that this approach not only complies with 2026 platform policies but often outperforms older segment-based strategies by focusing on proven customer actions rather than assumed interests.