I had a pair of jeans that I’d altered once. (Apologies if this explanation sounds simplistic, this is just how I describe things when I can’t physically point them out to people.)

There are two belt loops, just behind the hip, on your left and right side. You can conceal a small dart beside each one, disguising the fold under the belt loop. Alternatively, you can invert the trousers, don them while inverted, and pin down the outer hip-to-ankle seam and then stitch that into your preferred shape. This is easier to conceal and easier to tailor into a more flattering shape.

When it comes to altering the length, shortening them is easy. But if you want to keep the fold well-hidden, you can use hem tape to make a backing, to protect the stitches from forming an obvious crease. Granted, no one’s gonna be looking much at your ankles unless you have nice shoes or they have a thing for feet. But still, hem tape will help make the thread tension less obvious.