Cut out two pieces of leather, approx 5mm wider and longer than your tablet's front face. More if your tablet is fat. Sew three sides, with the outside faces of the leather facing inward.
Sew your lining to the open top parts of the sleeve, with the finished side facing out. Pin the lining on both sides to help with the next step.
Sew both pieces of fabric along the three edges that you've already sewn. The leather will now have been sewn twice to give it strength. Trim off any excess fabric.
Turn the whole thing inside out. Don't worry if the finished article is a little tight to begin with, the leather will stretch. Hey presto, an iPad sleeve made from an old couch.
Tell your friends your sleeve is a handmade Italian designer sleeve, and mock their neoprene garbage.