This article explains how to disable the bar that is always present in one of the corners of the Chromebook.
Disable the bar as follows:
1. Click on the time in the bottom-right corner.
2. Select 'Settings' (the gear icon).
3. Scroll down to 'Advanced'.
4. Scroll down further and select the 'Manage accessibility features' under the accessibility tab.
5. Disable the option 'Click automatically once cursor stops'. This option is located under 'Mouse and Touchpad'.