It really is possible to project these orthographic drawings of a house to isometric in less than a minute! I actually did it in 35 seconds!
This video gives an overview of the process using AxoTools in Adobe Illustrator. You can find the step-by-step instructions and link to the project file (saved for Adobe Illustrator CC 2019) here:
The technique highlights AxoTools’ project-in-place functionality using reference points for quick, accurate placement, ad well as extruding in an axonometric view, measured from a corresponding distance dragged in a flat ortho view.
This visual approach eliminates tedious measuring or counting of isometric grid units. Try it! If you don’t have AxoTools, you can download it here.