Pop In A Box Flash Sale: 50% Off – 1 Day Left! Posted by Hello Subscription on April 20, 2017. Subscription Box Coupons & Deals / Pop In A Box Coupons Hello Subscription may earn compensation via links in this post. Read the full disclosure Save for Later Notification Pop In a Box is having a flash sale! Through midnight 4/21 use coupon code NEWSUB50 to save 50% on your first box of ANY size (up to 12!).