I'm surprised by the anti-workshop sentiment, we have some slavers in the house I take it?

If you aren't using slavery and you need more hammers do whatever it takes to get them.
If you want the more effective improvement, then yes workshops stink before. If you aren't in Slavery, you're either in Caste (run specialists) or Emancipation (cottages or you already have enough technologies). If you're in Serfdom: more workers. If you aren't in anything: why aren't you in Slavery?
For reference:
Consider, you have:
-Metal Casting
On grassland a workshop is: -1f/+1h = 1

1

= plains tile = bad [pay 1 food for 1 hammer]
On plains a workshop is: -1f/+1h = 0

2

= un-mined plains hill = bad [pay 2 food for 1 hammer]
On flood plains a workshop is: -1f/+1h = 2

1

= forested grassland = somewhat bad [1 "free" hammer provided you have the happy/health cap]
Basically you're working low food unimproved tiles. You can do the math if you want to see the actual yield versus farms+whipping every 10 turns (or less).
-Add one of {Caste,Guilds,Chemistry}
On grassland a workshop is: -1f/+2h = 1

2

= forested plains tile = somewhat bad [pay 1 food for 2 hammers]
On plains a workshop is: -1f/+2h = 0

3

= mined desert hill = bad [pay 2 food for 3 hammers]
On flood plains a workshop is: -1f/+2h = 2

2

= lumbermilled grassland = somewhat decent [2 "free" hammers provided you have the happy/health cap]
This is slightly better but you're still behind compared to whipping. Not that I'd workshop a flood plains for 2 hammers... a cottage or a farm to pay for mines/specialists is far better in my opinion at this stage.
-Add two of {Caste,Guilds,Chemistry}
On grassland a workshop is: -1f/+3h = 1

3

= grassland hill mine = very good [pay 1 food for 3 hammers]
On plains a workshop is: -1f/+3h = 0

4

= plains hill mine hill = pretty good [pay 2 food for 4 hammers]
On flood plains a workshop is: -1f/+3h = 2

3

= lumbermilled grassland+railroad = pretty amazing [3 "free" hammers provided you have the happy cap]
If you're planning on playing peacefully for a while, it starts to pay off here. When you add the third choice it becomes better than mines! And when you add State Property... well you know how it ends up.
Or more simply, as DaveMcW put it:
Workshops stink before you have workshops? Are you sure?
Absolutely... since they can't be used

... thanks - fixed my post.