Which block requires the most steps to craft in Minecraft?

As of 1.8.9 I strongly believe that the minecart with hopper is the longest recipe. Unless you count banners. There are banners with all kinds of designs and depending on the design will depend on the steps. Although for this you are adding on to the same item to create a better or worse one.

The book and quill takes 3 steps -The enchanting table takes 3 steps

but no other 4 step items

As of 1.14, Lectern beats Hopper Minecart. Lectern takes 6 steps:

1. Log to planks
2. Sugar Cane to Paper
3. Paper and leather to book
4. book and planks to bookshelf
5. Planks to Slabs
6. slabs and Bookshelf to Lectern

I'm not sure it's fair, but you could add rabbit hide to leather to make it 7.

i think lodestone is one of the crafts that requires many steps

1. in a crafting table, put 4 stones in a 2x2 manner to craft stone bricks
2. make stone brick slabs
3. make chiseled stone bricks
4. make netherite ingot
5. craft lodestone with 8 chiseled bricks and the netherite ingot

(you can also mine nether gold and craft gold ingots using gold nuggets)

(if you consider crafting furnace to cook items, that would add to another step) (if you are using wood planks as fuel, that would add to another step)

there's another that you may like to consider: arrow of invisibility

1. use glass to make bottles (go to the end to get dragon's breath, and water bottles for brewing)
2. make fermented spider eye and make potion of invisibility (then use dragon's breath to make lingering potion of invisibility) 3.chop wood and make planks
3. make sticks
4. make arrows
5. craft arrow of invisibility

( if you consider crafting furnaces, eye of ender, blaze powder, pickaxes, crafting tables, armour, bow, fuel[coal blocks or wood planks], food or maybe golden apples to get to the end, that would be many crafting steps)

if you get sticks from dead bush, crafting of sticks won't count.