Oblique and isometric perspective

There are different ways of translating a three dimensional image into a two dimensional surface: basically we have: technical orthographic views, as you have been practicing in Technology, oblique or isometric perspective and linear perspective.

Here there's a very clear video connecting oblique and isometric with linear perspective.

Here you have a great graphic of perspective basics in Devian art.

You can use a geometric net of grid to make drawings in an easier way, as you already have there the three main directions objects will follow (height, length and width. You can use such a net for creating 2D compositions or as it is in this case, a 3D drawing.