How to stop my IPAD keyboard from minimizing to an icon?

The issue that you describe would suggest that you are using an external keyboard with your iPad - as, when doing so, the on-screen keyboard is intended to automatically minimise. While an external keyboard is connected/active, even when intentionally using the iPad's on-screen keyboard for input, it may be unexpectedly minimised. Whether this is intended behaviour, or a bug, is unknown.

If you are not using an external keyboard with your iPad, perhaps you have some other HID device (such as Mouse) or some other Bluetooth or USB accessory connected to the iPad? If so, this may the source of the problem - either due to unsuitability for use with iPad, or incorrect/conflicting device settings. If applicable, as an initial diagnostic step, disconnect each of these items in turn - the objective being to systematically identify the offending device.

Otherwise, ff your iPad is not operating as expected, try a forced-restart - as this will often clear an isolated software issue:

Force restart iPad (models with Face ID or with Touch ID in the top button)

If your iPad doesn’t have the Home button, do the following:

1. Press and quickly release the volume button nearest to the top button.
2. Press and quickly release the volume button farthest from the top button.
3. Press and hold the top button.
4. When the Apple logo appears, release the top button.

Should the problem persists after performing the restart, it may be necessary to reset your iPad settings. While this reset will not cause any loss of data, as a precaution, it is always wise to ensure that you have a current iCloud or iTunes backup before performing the reset:

How to back up your iPhone, iPad, and iPod touch - Apple Support

When you are happy to proceed, you can perform the reset from iPad settings:

Settings > General > Transfer or Reset iPad > Reset > Reset All Settings

If the problem still doesn’t clear, the next step is to reset the iPad to factory settings:

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

If you remain unable to resolve the problem, you would be best advised to seek assistance directly from Apple Support. You can contact the Support Team using the Support link at top-right or bottom-left of this page. Alternatively you can initiate and manage your support cases using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:

https://apps.apple.com/app/apple-support/id1130498044

You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to assist with troubleshooting:

Genius Bar Reservation and Apple Support Options - Apple

To stop your iPad keyboard from minimizing into a small floating icon, you need to return it to the full-size layout. There is no single setting to permanently "disable" the floating feature, but you can snap it back into place and minimize accidental triggers. 

How to Restore the Full Keyboard

Two-Finger Spread: Place two fingers on the small floating keyboard and spread them apart (like zooming in on a photo).

Drag to the Bottom: Touch and hold the small gray bar at the bottom of the floating keyboard and drag it all the way to the bottom edge of your screen until it snaps back into full size.

Use the Menu: If your keyboard has a "More" button (three dots), tap it and select Full. 

Why It Keeps Happening

The keyboard usually shrinks because of an accidental "pinch-in" gesture or specific settings: 

Apple Pencil & Scribble: If you use an Apple Pencil, the Scribble Feature may cause the floating keyboard to appear more frequently.

To stop this, go to Settings > Apple Pencil and turn off Scribble.

Display Zoom: If your display is set to "Zoomed," it can sometimes interfere with keyboard scaling.

Check this in Settings > Display & Brightness> Display Zoom and set it to Standard.

Keyboard Settings: For some users, turning off certain predictive features helps keep the keyboard docked.

Go to Settings > General > Keyboard and toggle off Predictive and Shortcuts. 

Are you using an Apple Pencil when this happens, or does it seem to trigger randomly while you are typing