Publish the week, not a permanent catalogue
A box round changes with what is ready. Put up this week's boxes with what is in them, and take last week's down. A shop that shows a fixed list all year teaches people not to look, and then you are back to answering what is in it by hand.
Write the contents in the description even when the photo shows them. People order from a phone on a bus and skim the words.
The cut-off belongs in the shop
Say the deadline on every box: orders by Thursday evening for Saturday delivery. Then stop taking orders by setting the stock to what you can actually pick. A box that is still orderable after the cut-off produces exactly one outcome, a customer expecting food that is not coming.
Collection and delivery are different products
If you offer both, make them separate options rather than a note in the order. The people who collect and the people who get a delivery need different instructions, and a field somebody types into gets missed on a busy Saturday.
Regulars are the whole business
A box round lives on the same forty households ordering every week. Because the order arrives in a chat, you already have the thread: message the regulars when something unusual is in, and ask the ones who skipped two weeks whether something was wrong. That conversation is worth more than any new customer post.
Keep a short note of allergies and dislikes per household. It is the kind of detail supermarkets cannot do and a small round can.