The picker asks four questions: what you have, how much time you have, who is building and which style the child likes. The material list is deliberately ordinary: a shoebox, an oatmeal canister, LEGO or blocks, paper cups, a cereal box, an egg carton, a plastic bottle, a tissue box, paper towel tubes, craft sticks, paper plates and a mason jar. Tick only what you have and the list narrows to plans you can build without a shop run. Every plan also lists extras such as tape, string, straws and a coin, so there is no surprise trip at 8pm.

Box-and-stick. A box, cup or canister is propped on one stick. A string pulls the stick and the container drops over the bait. Ladder-and-pit. A ladder leads to a card floor on straws or a rim; weight on the free edge tips it and the visitor drops into a box or jar. Rainbow slide. A ramp carries the visitor down into a catch cup with a one-way collar or flaps. Decoy house. A little cottage has a hinged door and two overlapping flaps inside. LEGO. A brick cage, tower or vault uses a sliding gate, a plate trapdoor or a propped lid. Cage or jar. A jar, bottle, cup or egg carton closes over the bait, or a funnel lets the visitor in and not out.

A trap needs three things: bait that a leprechaun wants, a trigger that moves, and a catch that holds. Most homemade traps fail at the trigger. A box propped on a fat stick will not fall; a card floor taped on all four sides will not tip; a door that swings both ways is not a door. Build the catch first, then add one moving part, then test it three times with a coin and a small toy before bedtime. If the trigger needs a hard tug, loosen it. If it fires when you breathe on it, tighten it. The plan sheet has a box for the child to sketch the trigger, which is the part they will explain at school.

Leprechauns are supposed to love gold, and a shiny coin is the bait most children already have. Chocolate coins, shiny buttons, green glitter, rainbow candy, beads, a tiny mirror and a miniature shoe all work because they catch the eye. Put the bait deep inside the catch, not at the entrance, and put a second piece on the trigger so the visitor has to step on the moving part. Do not glue bait down: a leprechaun who cannot pick it up will not stay. Skip peanuts, small magnets and real jewelry, especially in a house with pets or toddlers.

The picker sorts by 30 minutes, an hour or a weekend. The 30-minute plans are the propped cup, shoebox drop, egg carton clam and jar snap: one cut, one prop, one piece of tape. The one-hour plans add a trapdoor, a ladder or a rainbow ramp. The weekend plans include the two craft-stick builds and the LEGO builds. Age matters more than time. Ages 3 to 5 decorate and place bait while an adult cuts and ties. K-2 can build the trigger with help. Grades 3 to 5 can own the build, measure the parts and write down what changed.

Every plan has a one-page plan sheet with a materials checklist, numbered steps, the trigger explained in one sentence and a box to sketch the trap. Print it, put it on the table and let the child tick off the parts. The free kit adds six signs, a ladder strip, a rainbow ramp, 24 gold coins, shamrock bait, a mini hat and a buckle. The footprints stencil, the leprechaun note and the coloring pages cover the morning after. If the trap comes up empty, the escaped note explains it without blaming the builder. Teachers can print a plan and a STEM worksheet for every child; everything is free during launch.