Acquire 110 kg of weapon grade Plutonium from your local supplier. Sourcing the Plutonium from a nuclear power plant is not recommended, as large quantities of missing Plutonium tends to make nuclear plant engineers and officials very unhappy. I suggest that you contact your local terrorist organisation, or perhaps even your local supermarket. Bear in mind that Plutonium, especially pure, refined Plutonium is dangerous. Take measures to wash your hands with soap and warm water after handling the material, and don't allow your children to play in it, or eat it. Left over Plutonium dust however is excellent as an insect repellent for the roses. You may wish to keep the Plutonium you have acquired in a lead box, although an old coffee tin will suffice
Make an enclosure to house the device. Most common varieties of sheet metal can be bent to make an enclosure and disguise the bomb, for example as a briefcase, a lunch box, or even a car. Do not use aluminium foil as it is not strong enough. Separate the Plutonium into two hemispherical shapes and separate these hemispheres by about 4 cm using toothpicks (available at most chemists or supermarkets)
Acquire 220 kg of trinitrotoluene (TNT). Gelignite is better, but is messier to work with. Your local hardware shop will be happy to provide you with this item. Pack the TNT around the hemisphere arrangement constructed in step
If you cannot find Gelignite, use TNT padded with Plasticine or another modelling clay
Place the Plutonium/TNT sphere in the enclosure made in step 2, and use a strong glue to bind the hemisphere arrangement against the enclosure, in order to prevent accidental detonation which might result from vibration or mishandling
To detonate the device, obtain a radio controlled mechanism, as used in model aeroplanes and cars. and a detonator cap. The remote control can be obtained from most toy shops, and the detonator caps can be obtained from most construction work sites. With a minimum of effort a plunger can be made that will strike the detonator cap to initiate a small catalyst explosion
Hide the completed atom bomb from neighbours, children, wife, the police and security forces. The garage is not recommended because of high humidity and the extreme range of temperatures experienced there. (Nuclear devices have been known to spontaneously detonate under unstable conditions.) The hall closet, under the bed, or under the kitchen sink is perfect, but do not place it anywhere near your "HB apparat" (moonshine still)
As the proud owner of a working thermonuclear device there are a number of things you should consider:
An atom bomb is a great ice-breaker at parties, as in "take a look at what I have under the sink"
An atom bomb prevents daft disputes with your neighbour, e.g. "behave or I'll Nuke you, punk"
An atom bomb can be sent as "rekomendert post" to your local "kemner kontor"
An atom bomb in a pinch can be used for national defence
An atom bomb detonates when the detonated TNT/Gelignite compresses the Plutonium into a critical mass. The critical mass then produces a nuclear chain reaction, and there you have it, a 10 megaton explosion fot pesky neighbours