How to Make It
Combine currants and lemon juice in a small bowl; let stand at room temperature 1 hour. Drain currants, and set aside.
While currants soak, bring 1/2 inch of water to a boil in a large pot over high. Place chard in a large steamer basket. Place basket over boiling water, and cover. Reduce heat to medium-low, and steam until chard has just wilted, about 10 minutes. Stir in cilantro, mint, and parsley. Cover and steam until herbs have wilted, about 3 minutes. Remove herb mixture, and spread in a single layer on a rimmed baking sheet; let cool 10 minutes. Squeeze cooled herb mixture to remove excess water; finely chop.
Heat 3 tablespoons oil in a large skillet over medium-high until shimmering. Add coriander and Aleppo pepper, and cook, stirring constantly, until spices smell fragrant and darken, about 10 seconds. Immediately stir in chopped herb mixture and chopped thyme; reduce heat to low. Cook, stirring often, until moisture evaporates, about 10 minutes. Stir in salt, preserved lemon, 1 tablespoon oil, and drained currants. Remove from heat, and let cool completely, about 30 minutes.
Shape mixture into 24 (11/4-inch) balls (about 1 tablespoon each). Place 4 herb balls and 4 feta cubes in each of 6 (8-ounce) jars with lids. Pour in enough oil to cover mixture (about 1/2 cup per jar). Place 1 smashed garlic clove, 1 thyme sprig, and 1 lemon peel strip in each jar. Attach lids, and refrigerate at least 4 hours or up to 5 days. Bring to room temperature, about 30 minutes, before serving. Serve with crostini or crackers.