How can you make gelatin at home?
After a quick Google I found this recipe :- http://www.grassfedgirl.com/diy-make-your-own-healing-gelatin/


  Ingredients:
  
  
  3-4 lbs pastured animal bones (any kind will work, I even mix them between animals) (the more bones the more likely it will gel…fill’er
  up! )
  4-5 quarts filtered water
  1 tbsp sea salt
  
  
  Directions:
  
  
  Put all the ingredients in a slow cooker over night or for up to 48 hours.
  Strain it off through a wire mesh strainer.
  Refrigerate until firm or overnight.
  Chip or scrape off any fat and save for cooking or discard.
  Melt the gelatin and add fruit and sweetener to make something sweet the refrigerated again.
  
  
  Or use the gelatin as a base for making a soup or stew.
  
  This gelatin will keep in the fridge for a week (or a year in the
  freezer.)


One thing to note, the recipe makes no mention of all the meaty juices which will settle to the bottom during the cooling process. So where it suggests scraping the fat off the top I would recommend flipping the big gelatin block over a slicing the bottom off also.

Also during the straining process, if you can get hold of some cheese cloth or muslin it'll help ensure there are no meat particles in there anywhere.