Use single spacing and justified margins

Style note²Federal courts, Illinois courts21st and 22nd editions

A block quotation is drawn single spaced and squared off at both margins, so it reads as borrowed text rather than the writer's own paragraph.¹

1. 1B5.2 Block Quotations. Tables: R. 5.1(a)(i) Indentation and quotation marks.
2. 2A style note: the rule in note 1 allows both forms and prefers one.