I meant this as a joke but I think I’m going to make this serious.
So first, what you want to do is rob a blacksmith village or get iron yourself. To make this even harder, you should try (demonitized) an Iron Golem. Next, what you do is, (depending on how much iron you have), an iron pickaxe and water bucket. Next, dig straight down using the 1 by 2 trick by standing in the middle and digging one side down. Head straight for Y11 or Y5 where diamonds are most common. If you press F3 on Java Edition (PC), you can see what coordinates you’re at. On bedrock, (C++ coding, Xbox, PE, Windows 10, etc.) typing in the chat, “/gamerule showcoordinates true” will show you your coordinates on the top left hand side. Once you’re at Y11, start strip mining around unless you find a cave/ravine. Try not to (demonitize) yourself. Diamonds can be found near lava. If you need to cross lava, place your water on the coastline of stone to make an obsidian bridge across the lava. Grab your water back. If no diamonds found, start strip mining again.
I cant see the point of this just beat the game without diamonds.