This is how I learned it:
Begin with a mod that adds items into the game.
Step 1: make your art.
You only need to go as far as to have a model.
Step 2: Get your model in the game.
For this, you download the starter_mod_basic, which has all the functioning mechanisms you need. Then, you simply and only replace the wooden piggy bank with your item. Remember that your item even needs to be called wooden_piggy_bank.qb, or whatever the name is. Then you can install it in your mods folder and see your model in the game.
Step 3. Get to know your material
A good exercise (that is, the exercise that helped me a lot, there might be better ones) is to now start morphing the startermod into your own, complete with name changes of the folders and and ending with the name-change of the mod. At the end of step 2, you’ll notice you had only a bare-bones version of your model in the game, no representative recipe, no iconic form, etc. You do this exercise to learn how everything is interwoven, how all the references play out, and what is specified where. Tip: I highly recommend morphing one detail at a time, and checking if you haven’t broken stuff every time you change something. If you have broken stuff, you should fix it immediately, both to know what you are doing wrong (might sometimes be little typo’s), learn how to fix it, and to not loose focus to other things, which will make everything look more complicated.
Step 4. Learn how to steal.
If the item you had in step 3 required a separation between a placed version and an iconic version, you’ll probably already have done this, (I believe). What I mean is this. For every featurre that is not in the mod, you look at how the stonehearth main mod does it. (this is stonehearth.smod, and you have it in the mod’s folder if you have stonehearth itself, it is what stores the game.). For this you use your knowledge of the behaviour of vanilla stonehearth items. You simply copy the tactics, fix all the references for what you need, and then it should work.
Step 5. Search and ask on the forums.
If you really don’t come any further, you still have the forums. search first if some other modder has run against the issue before (I know i have my share of threads hunting for annoying-bug-hunting threads). And if not, you can always ask.
With all that, I want to say: Good Luck.
P.S. .jsonlint is your friend in catching .json typo’s