Help! This is a sewing question....

I have almost zero spatial ability and when I sew things, I cannot believe the item will turn out the way it says... it does. For example, making pants - turn one leg inside out and put it in the other and sew the back to front - who'd figure it'd work, but it does.

Anyway, I'm having a problem figuring out how to make a reversible or lined eyeglass case. I have tried most every which-way to do this but nothing is working and I'm getting so frustrated.

How do you line up the fabric? Do you leave an opening somewhere to pull the whole shebang through, or what???

I am going to use one long piece for each of the outside and the inside (lining), fold them at the bottom, and sew up the sides, leaving the top undone, to be sewn last. At least, I presume that's the most logical way... what do you think?

Do I need to turn under the top sides first, then sew the sides? Do I leave an opening somewhere to pull the fabric through?

I'm taking my nephew to work, but I'll be back in a bit...

Thanks for any and all help.