Basic concepts behind Faraday cages are documented on many web-pages. A successful implementation requires access to certain conductive materials and getting your priorities straight. In principle you can annihilate radio fields with frequencies in the range of WLAN, 4G, 3G and below (appliances, FM, AM).
The principle is used in security rooms in basements of embassies, where you protect against eavesdropping and still maintain a temporary working environment. Electronic firms use the concept in development and service of their products and there are other situations where you need to protect ordinary working conditions and privacy ignoring the possibilities of eavesdropping with conventional tools (outlets, windows, microphones)
To reduce radio fields you need to apply layers of metal wire mesh (copper, iron, galvanized iron) The higher conductivity the greater reduction of the radio fields and the smaller distances between wires the greater protection from high frequency fields.
Grounded meshed copper blankets connected with magnet strips/soldering offer the most optimal protection. Two layers of grounded meshed shields with orthogonal orientation reduce 4G fields significantly.
Smartphone with WLAN effect scale (red weak, green acceptable) uncaged. -80dBm
In principle you should be able to construct a cage (one or two layers) by crafting a cube in wood and attaching a mesh of copper weelding wire. The project can be divided into three steps: 1) Building the skeleton 2) Attaching the wire (place yourself and/or a cell phone with measuring apps and a FM radio app inside the cube to test the result 3) Constructing a door or entrance without compromising the conductive abilities of the cage (initially you can use a grounded iron plate as floor). Other people use spray painted walls to secure rooms, e.g. concrete holes in workshops with painted surfaces and an iron plate on top.
Smartphone with WLAN effect scale (red weak, green acceptable)-90dBm
Closed cage with contact between mesh and phone
Smartphone with WLAN effect scale (red weak, green acceptable)
Open cage with contact between mesh and phone - the mesh has no effect.