You have multiple ways to hard reset the Iball Slide tablet.
Iball Slide series has both Windows and Android OS installed depending on the model. As your question is not specific for the Android or Windows installed on your iball slide so listing both the ways to factory reset the device.
Using Recovery Menu You can use this method for the iBall Slide's android tablets.
1. Press the power off button.
2. Hold the volume key till it shows the recovery menu.
3. Select factory reset from the menu option.
4. Tap the power button to activate the factory reset option.
Note this recovery menu's option will reset all the data from the device. If you are using any ROM Mod then you have even better option to do this quickly. That being said, you can also factory reset the device from inside the OS options too. Follow the steps if you wish
1. Go to "Settings".
2. Go to "Backup & Reset".
3. Select "Factory Reset".
4. Tap the button that says "Reset Device".
This will accomplish the same task as the above recovery menu.
Hard Reset if the OS is Windows 8
If you have Windows 8 installed on your iball Slide then follow the steps below to hard reset the device.
1. Tap into the Settings Page.
2. Tap onto the "PC Settings".
3. Tap on the option "Update and recovery".
4. Tap on the link that says "Recovery".
5. Find the line "Remove everything and reinstall Windows" and tap into "Get started" button.
This process will start the factory reset. It removes all your personal settings, files and configuration. You get the device completely clean from settings.