I found a tutorial on hairglamourista.com that explains how to cut an inverted bob step by step. Here are the steps:

1. Wash hair thoroughly with a shampoo and a good conditioner. Dry with a hair dryer.
2. Now, make your friend to sit in a good chair facing the mirror, or place a dummy in a similar manner.
3. Start sectioning hair in the standard way.
4. Now, start with the back hair first.
5. Go to the side sections now.
6. Cut the hair in an inverted manner.
7. Use thinning scissors to blend the hair.

You can find more detailed instructions and pictures on the website . I hope this helps!