You don't need much in the way of woodworking skills for this either - you just need know how to nail and screw things together.
NOTE: if you going to make this type of bench make sure your floor and walls are reasonably level, straight and square to each other or you won't be able to swing the legs out evenly.
Step 1: Select your wall
Step 2: Build the legs
Things to watch out for:
1) Make sure the gap at the top of each 'leg' is big enough to accommodate your wall fixing (in my case it was a length of 2x6 timber upon which I hung the bench). The area I mean is shown by the green arrows.
2) Make sure the legs are less than half the width of the bench you have so that they will fold in without obstruction. It's important they're about 4" shorter than half the width of the bench so they've got space to fold out and still be under the bench (not beside it).
3) Also make sure that the width of each 'leg' is of course not more then the depth of your bench or they will stick out the front.