I have a pair of trousers from a brand named apricot. The legs are not sewn together but overlap and are floaty lovely. they have an elasticated back waistband.
Should be easy to draft from a regular pair of pants.
Line up the side seams of front and back leg patterns, spread out flat. Trace the back pattern, and include about 1/2 of the front pattern. Then repeat for the front, adding about 1/2 of the back pattern.
Cut from fabric, hem the loose edges, then assemble.
Just because I didn’t see it listed yet: this type of pant is often called “Thai Fishermen’s Pants,” and searching that term will turn up a TON of free patterns, tutorials, and walk-throughs on websites, as well as actual patterns, such as " Simplicity Easy-To-Sew Sewing Pattern 8134," which includes an elasticized waistband on the stationary/front part of the pants, rather than the double wrap version that is more traditional (and also, yes, exceptionally hard to go to the bathroom in carefully in a public place). .
Untie the front, swoop it up and bunch it about at your belly. Sort of like what you would do with a long skirt, I suppose.
I have one pair that I really love wearing in summer.