Can Muslim women wear long skirts with a slit?

The rule behind it

Scholars agree that in front of non-mahram men, a Muslim woman covers her body except (in most views) the face and hands, with loose, non-see-through clothing. The legs are part of what's covered. The Quran says believing women should:

So the question isn't the slit itself, but whether skin or a tight outline shows through it. See Can I wear tight or see-through clothes with hijab?

When a slit is fine

• Layered over trousers or leggings that aren't skin-tight. Many hijabis wear slit maxi skirts or abayas over wide-leg trousers.
• Small walking slits at the back or side that only open a few centimetres and show a lining or an underskirt.
• Pleated or wrap skirts where the overlap is deep enough that nothing opens when you move.
• At home or with women only, where the rules are much more relaxed.

When it's a problem

• High thigh slits that open with every step.
• Slits worn over bare legs or sheer tights.
• Slits that only look modest standing still but open when you sit, climb stairs or get in a car.

Do a quick test in front of a mirror: walk, sit, and bend. If skin shows, add a layer or have the slit stitched up partway. A tailor can do this cheaply.

What about feet and ankles?

Scholars differ on whether the feet must be covered. The majority (Maliki, Shafi'i, Hanbali) say yes, while the Hanafi school allows the feet to show. Long skirts with socks or closed shoes cover both views. See Do I have to cover my feet as a Muslim woman?