Seems like it could have been laid out fairly plainly from early on.

One block to someone who is "owed" a block for every "x" number of blocks produced, with the back ordered blocks being delivered in order of those who paid first, get theirs first.
Once the production levels had become somewhat known(x number of finished blocks being delivered per month), then a schedule for filling the back orders could be established, along with projected delivery dates for each of the people waiting.
Then it's just a matter of letting them know when their block is projected to be done.

*If you are an existing Customer, or if you are waiting on an Order*

If you have an existing order, it will be delivered.

Our Dealer network is taking over the management of your order and will be your single point of contact. Contact information for our Dealers is set out below. If you haven’t contacted already, you will be by Friday January 27. Your Dealer will advise you of your exact date for shipment (all open orders now have a specific completion date assigned).

Initially, we have some backfilling to do but we expect by mid-year to be well and truly ahead of this with plenty of blocks in the market with Dealers and customers. Blocks start shipping to Dealers on January 27.