A feature of the cosmetic bag is its shape. I hope you'll like it :)
You need these materials:

Join fabric and the base, pin them together:

Add the zip:

And the lining with face down:

Stitch:

Carefully cut the base out of the seam with scissors:

Stitch the edge:

Treat the second edge the same way:

Sew the zip in. Turn the blank with the lining out:

Pin one side:

Stitch:

Cut off the protruding ends of the zip and extra fabric:

To cut out a small strip of fabric to perfect the side:

Stitch.

Iron this way:

Pin the corners this way:

And stitch:

When the edge is ready, turn the bag outside in:

Now make a loop:

Iron:

Treat the top side of the bag the same way:

Stitch and remove the excess:

Pin the loop:

Do all the same:

The cosmetic bag of an unusual shape is ready! Put your mascara and lipstick inside ;) Thank you for attention!