A single large block has significantly less surface area exposed to warm air than an equivalent weight of small cubes. Tests show block ice can remain intact for 3 to 5 days longer than cubed ice in identical conditions.
For massive quantities (up to 300 lb carving blocks), look for local distributors like Ice Boy or regional ice companies that supply restaurants and event planners. The Efficiency Factor: Why Block Ice? where to buy block ice
If local stores are sold out, you can easily manufacture "blocks" at home. A single large block has significantly less surface
Locating block ice requires knowing which retailers prioritize "hard" ice products over standard convenience bags. where to buy block ice