How do you plan an ESP class to skilled workers who have zero English language knowledge?

ESP stands for English for Specific purposes. Meaning, there is English for Doctors, English for Nurses, English for Engineers etc.

Now the question is how to plan a class for employees who have zero knowledge in English. 

My answer to that is starting with the basic - back from scratch - like how the first language is acquired. Meaning, you begin with the letters of the English alphabet. You teach  them how each letter may sound. For instance in teaching the letter "a" you must provide the different ways the letter can be sounded in the English language then you give examples.

If you see that they can sound well the letters of the English alphabet you may move on to teaching them words that are a bit difficult to say and spell. 

If they can catch up with words difficult say and read and spell, you can teach them phrases or idiomatic expressions, then sentences. For them not to bebored, you may utilize English movies in teaching idioms so students can hear how words are said by native speakers of English, andat the same time students won't get bored.

If students can somehow speak English, though not that proficient yet, you may move on in teaching them business Englishor ESP.

Teaching any language needs patience and creativity. You may teach and learn the language by having fun. At the same time, camaraderie among the groups will be strengthened. But don't forget to have fun!

It is not difficult to plan or orientation or coaching any skilled worker for Language courses as long as they are adaptable, willing to learn, Urge in their mind to know new languages which will be of help in the future, Right Attitude