Firstly, why do you want to go for the egg industry, and what are the advantages of it.

• This industry may or may not need any planning, it is relatively very cheap and it is capable of bulk cooked meal production of all grades to keep dwarves happy.
  
• When I say that it may / may not need any planning, it means that you can embark with a bunch of chickens and a rooster or you can simple obtain it later in the game or with migrants.
  
• Egg in a barrel, pot, metal or anything is a very good trading commodity. with 10's of egg laying creatures laying eggs, it becomes a bulk trading supply. The more the variety, the better it is for dwarves to eat and for trade. It becomes an egg barrel.
  
• The item is not to be traded with elves, dwarves and humans only.
  
• Very, very easy to set up and execute. Any player can do it. This is capable of a bulk leather industry as well. but that is something at the end of this guide.

Now let us make an egg industry

• You need egg laying animals, from a chicken to a duck or anything of that kind. Male Female pair or at least one male with lot of females. I'd go like 5 hen and one rooster.
  
• Then you go to any workshop that makes nest boxes and make nest boxes.
  
• A craft-dwarf, kiln, glass-maker, forge make nest boxes.
  
• Now you want to make a small room or a medium room.
  
• In this room we place nest boxes.
  
• We press zone and place a pen/pasture zone on this room.The room better have a single door entry.
  
• Now in this zone we have nest boxes and a pen/pasture zone on it. In this pen pasture zone, we place the egg laying animals. Their male female that is.
  
• Now the eggs will begin to lay.

Reference :


More references.


Because the room is locked here, the eggs are available. Now the room is locked so no dwarf will come and take the eggs for consumption and these will hatch wonderfully. There by we will have 1 :20 : 20x20 more king cobras giving us a delightful king cobra room . So this will be like a legit venomous snake room type thingy. I will update on this later !

Now there is a point where you have a lot of eggs but no meat or leather or bones. Not that meat and bones are a high demanded commodity but it is a good thing to trade or to make crafts from. Leather on one hand can be used to make stuff, useful stuff.

Now how to let these eggs hatch to get a very high population of egg layers that they can grow up?

The answer is in locking the nest room door.
This is how a door can be locked after clicking it :

And now the room looks like this :

So now when the eggs are laid, no dwarf will go and pick it up. Eggs hatch, creatures grow like... one hen lays 6 - 7 eggs, so 6 - 7 chicken, then they lay 6 - 7 eggs each. There we go 36 chickens considering you started with one rooster and one hen. Now butchering 36 chicken gives nice roasted meat, stew, biscuits, bones, chicken leather to make clothes and all.

That is a partial leather industry in itself. Full fledged leather industry is another thing in itself.

Will post more pictures, any doubts then comment. I will answer them.
Just so you know certain animals like elk birds for instance are quite exotic and very, very hard to get to have baby elk birds. So go on simple sweet small animals, good luck.