1. Switch off the tablet by holding the Power button.
2. Afterwards, press & hold together Volume Up + Power button for a while.
3. After you feel the vibrations, release the Volume Down and press Volume Up key.
4. Release held keys when Boot Mode appears.
5. A new menu will appear onscreen. From it, select t Fastboot by using Volume Up to scroll and Volume Down to confirm.
6. Good job, you now should be in the Fastboot mode. Probably.