Most of New York City’s galleries are clustered in districts. (See the lately ballooning scene in Tribeca.) But some spaces are destinations in themselves. Two decades ago, in Brooklyn’s Bedford-Stuyvesant neighborhood, the insightful Ivy Jones opened Welancora, a Black-owned gallery anchored by the work of Black artists, long before every big-box gallery in town began jumping on the diversity bandwagon. In the airy parlor floor of a brownstone at 33 Herkimer Street, Welancora is showing (through May 7) the abstractions of Carl E. Hazlewood, a Guyanese-born American artist, who is also an accomplished curator and writer. In Hazlewood’s hands, simple means—plastic mesh, cut paper, pushpins, fabric, metallic string—assume formally and intellectually complex dimensions.