The energy at Fairview Market Hall in South Lake Union earlier this spring seemed reminiscent of an early 2000s shopping mall on a Sunday: Packs of visitors perused vendors’ tables and carts and sampled a vibrant selection of food and drinks, from baked goods to coffee and matcha. Hundreds of attendees flocked in March to THE BLOCK , a free event that gathers local pop-up cafes and businesses at one central location. The second iteration on Sunday will host more than 20 pop-ups, and guests who RSVP before the event can try free samples in addition to shopping vendors’ menus, said Michelle Dean, the event’s organizer and co-owner of Bonhomie Coffee Bar . “Because of the volume of pop-ups that are showing up in the city, it’s hard to keep up,” said Dean, who added she wants to make the gathering happen quarterly during the year.…