Inspired by 1960s and 1970s music, "Slow Dancing" is an acoustic, mid-tempo pop, rock and indie folk ballad, with country music influences and minimal, "stripped-down" production. Billboard's Lindsey Havens labeled it "contemplative, California-rooted rock". Lasting four minutes and twenty-seven seconds, AJ described its production as "warm and inviting". AJ performs lead vocals, with her and Aly trading "hushed", "dreamy" harmonies that emphasize the romance of slow dancing with a significant other. Justin Moran of Paper noticed that "Slow Dancing" is remarkably "softer" than the duo's two previous electropop singles, "Attack of Panic" and "Joan of Arc on the Dance Floor", both released in 2020, although the ballad retains some synth-pop traits. As one of the album's slower tracks, Gabriel Aikins of MTV Australia observed that Aly & AJ's pop origins are replaced with intimate guitars. Featuring relaxed guitars, gentle drumming, soft percussion, a steady bassline, and calming lyrics, "Slow Dancing" begins simply with a guitar riff layered underneath their "dreamy" vocals. The second half of the song features "more robust" production, with additional instrumentation including organ, cello, and saxophone. Music critic Thomas Bleach cited influences of doo-wop as the song steadily builds towards a guitar solo. Certain critics have likened "Slow Dancing" to the work of country singer Patsy Cline, rock band Fleetwood Mac, and pop singer Taylor Swift.
