When using this seed, you will spawn in the mesa on the seashore. Many mines can be found near the spawn point. The entrances to them are clearly visible along the rails that come out to the surface. You can get a lot of resources and find chests with loot right at the start of the game.
How to use Many Mines seed
Start the Singleplayer mode
Select ‘Create New World’
Then click on ‘More World Options…’
In the ‘Seed for the World generation’ field, enter -823866603