How to make injera using just teff flour and water...

Natalie here is an earlier thread about injera with some helpful ideas
https://food52.com/hotline/25284-does-anyone-have-experience-advice-for-making-injera

Make a starter first. 1 tsp off teff and one teaspoon water. Ferment for 2 days. Then throw out half of it. Add a teaspoon of water and a teaspoon of teff. Ferment for a day. Throw half on the next day, and add another teaspoon of teff and water each. Do it for a week or two. When your starter is active and healthy, build it up to the amount you wish to have.

To save your stater, save in a non reactive glass jar and feed weekly. Be sure to throw or use some so the ferment is always fresh.

Alternatively, you can convert an existing sourdough starter into teff. Mix a cup of teff with a cup of water. Add a teaspoon of an active sourdough starter in. You should have a healthy and active teff starter in a few hours.

Shauna James Ahern has an excellent recipe for injera in her cookbook "Gluten Free Girl Everyday". Her batter recipe only has to sit for a minimum of an hour, but can rest overnight as well. She suggests that the reason why injera doesn't work with the teff flour available in the US is because it is different from the teff available in Ethiopia. Hopefully you have access to this cookbook - because not only is this recipe great - the whole thing is!