A background - I've used a canvas that I had hanging around, but you could use any piece of stiff board, MDF, or similar
Step 1: Prepare the background
Get the background painted, and pop to one side to dry off.
Step 2: Make the butterflies
Once I'd got my sheet of templates printed, I drew round them on coloured card, and cut them all out.
To give the 3D effect, I folded the wings along the edge of the body, leaving the body flat.
Step 3: Get sticking
Once it's all dried, either find a nice big bag to gift it in (I wouldn't recommend wrapping - you'll squish the butterflies!), or find a bit of wall to hang it on... It'll look best somewhere that sees a bit of light, so that you get shadowing around the wings.