How do i make an anvil in minecraft properly?

for plain repairs you don't always need the anvil. two worn copies of the same tool in the crafting grid, or in a grindstone, merge into one with the durability added together - but both of those strip the enchantments, so only do it on unenchanted stuff. anything enchanted, anvil every time.

31 iron for the thing itself - three blocks along the top, one ingot under the middle, three ingots across the bottom. what actually catches people is after that, because the cost goes up every single time you use it on the same item, and once it asks for more than forty levels it just refuses. if you're stacking enchant books, combine the cheap books with each other first and put the finished book on the tool last. saves an absurd amount of xp.