I created this multi step form without the Webflow built in slider component.

Solution: 
You can create easily a form and basic interactions to hide and show each steps in a row to click the back and next buttons.

Nothing fancy just working properly and fine

The main issue with the form combine with the slider component is that you don't have to set up the height for each step of the slider independently.
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Back and next buttons exist outside the mask which hold the slides. Thus you don't able to control the buttons slide after slide. If you have different height slides you get a big white space in the lower slides which is out of your control.