Gift boxes
Create a gift product with an option such as Gift and values like 1 box, 3 boxes and 6 boxes. Add the Gift a box section and choose it: shoppers pick a length, write a gift note and pick a send date, and both are saved on the order as line item properties.
Recurring billing
Prepaid plans work without any app. For monthly recurring billing, install a subscriptions app such as Shopify's free Shopify Subscriptions and add your box to a subscription plan. Add the Subscribe and save block to the product page and Crate shows the app's plans next to the one-time option automatically.
One-off boxes and add-ons
Use the item product template (Product → Theme template → item) for one-off boxes and add-ons: it leaves out the plan comparison and cutoff.