I want to create some furnaces, but I don't know how. So, how do I create a furnace?

Look at the classes, BlockFurnace, TileEntityFurnace, GuiFurnace, and ContainerFurnace

ScratchForFun has a very good tutorial on how to create a furnace from scratch

https://m.youtube.com/channel/UC786-fvOTMkndZPRwr15zVA

 

His channel is a bit messy so you might have to look around a bit.. The furnace series is 27 videos.. Good luck!!

@ovikk Can you give the links for the videos instead of a link for his channel?

Never mind...

 

But is there a text tutorial?

I think you can skip some parts, if you don't want to understand the whole thing, but I don't recommend this way.

@DeltaDrizz Which parts can I skip???

@ovikk Can you give the links for the videos instead of a link for his channel?

There is a playlist on ThePizzaBoyHD's channel..

 

@DeltaDrizz Which parts can I skip???

ScrathForFun basiclly copies the entire vanilla furnace and creates his own "quartz furnace", while explaining everything. You should only skip stuff you know you understand and can manage on your own 

@ovikk Thanks! But does it work for 1.7.10?

The tutorials are for 1.6.2 but with some work you could get them working on 1.7.10. But like Jedispencer21 said take a look at those classes.

@ovikk Thanks! But does it work for 1.7.10?

Yes it does! 100%! You only need to follow Jedispencer21's advice and look in the vanilla's furnace classes when theres something you do not understand!