Low Poly Style, How to make it?

Hello friends, me and my friends in the University are trying to make a game and I'm the responsible by the Modelling and etc. We decided that we are going to make the game in the low poly style:

imgur.com/a/BAx1u1z

I particulary love this style, but I have a little problem, I dont know how to do this (and my teacher hates this Style of modelling, and dont know how to do also), so, I would appreciate so much if someone could help explaining me how to make this type of style, or if you know of a tutorial that can explain this (I searched, but by the most, they just shows a speed run or how to make a specific object).

Thanks to all of you in advance.