marked out the red line as your guide where to cut the cardigan. You can used marker/fabric chalk to draw the line. I'm just cutting blind.

remove the sleeves and

Then, Cut the main part of cardigan as show in the pictures.

cut in the middle of upper top of the cardigan

# Now I'm showing you guys how to re position all the pieces that you cut earlier, now I hope you can see the legging already take shape...
# Owh do you see the shoulder part from the sleeve
cut it so you have straight line and much easier for you to sew it later.
# Everything will be clear in pictures below.

#1. will be your waist and butt...
#2. will be ur tights and bcoz of the natures of my cardigan have big opening in the front I need to cover the small opening with
#3 shoulder part that we cut earlier lastly
#4 is your leg this cover from knee below..
then the only thing you have to do pins and sew to put it together.

# done with sewing and you can wear it like harem pants or you also can trims at tights areas to make it more fitter and straight leg... and then you done...
if you thought at waist areas will be loose you always can put elastic band...and tara... its done..all this process took me 1 hour to finished.. Good luck...peeps..

the results

Wear it as a legging or as a comfy PJ..

If you making this plz show me ur pictures.