First start with a shoe box and cut a door/flap out of one side.
Everyone knows that a Leprechaun is attracted to shiny things. We used LOTS of sliver glitter and bright colored paper. I cut a piece of paper to be glued into the bottom of the shoe box and we cover it with glitter. You could use tin foil or just let your kids color the inside. 
Get crazy in your decorating! I think the more the better for this particular craft! you can see we have used a lot of glitter... I think mirrors and stickers would be really fun too!
Then you will need to make the trap/maze part of it. I did not measure anything. I just eyeballed and cutout a bunch of pieces. *USE a HOT GLUE gun to put these pieces in. It was the easiest way for me to get it done! And it held up really well! 
Then cover the top with plastic wrap so once his gets in he can't get out, and prop the door open with a toothpick.This is the Leprechaun's view... my son had a great idea to make an arrow to make sure he knew which way to get in!
Set it out and see what you can catch. We didn't get a pot of gold, but we did get some Pop Rocks and through out the day we kept find little gold coins. He even came in and got out while we were in the room! So build it well cause they are tricky little guys!
May the Luck of the Irish with you!
Then, I pained some little wood letters and before the paint dried, I dipped them in some green glitter... I think those foam stickers would work too. For this craft, you will need enough to spell out "LUCKY CHARMS" 
I had two different kinds of St. Patrick's Day ribbon... I went with the green kind, But whatever you have or can find would be way cute! Hot glue to the bottom of the board, but make sure you wrap the edges around all the way to the back, so it wont fall off easily.
Then I just hot glued the clovers to the top of the board, so the top half would stick up above the board. 
