Wicking beds are permanent garden structures that come in a range of sizes. They are now made from a diversity of materials and structures. (Click here for Other wicking beds.)
They all have the following in common:

Above ground structures
They are mostly above ground level. This makes them easier to work with. It also protects them from flooding and water-logging during extreme wet weather. We had crops doing well, while we sloshed ankle-deep through water between the beds.

Impermeable liner at the bottome and sides
They have a water holding plastic liner at the bottom, turned up along the sides to at least 150mm, preferably 300 or more. Many people now have the plastic to close to the surface.

Water reservoir
They have a water resevoir running lengthwise along the centre of the bottom. In many cases the reservoir is made of 90mm PVC drain pipe, but sometimes from other materials.

Fill pipe
They have a fill-pipe, often also 90mm PVC, connected to the reservoir through which to fill the reservoir. This allows watering to be done mainly from the bottom up, rarely from the surface.

Overflow point
They have at least one place where the liner is pushed down to 100 to 150 mm from the bottom. This is absolutely essential to provide drainage of excess water during heavy rain or over-watering. Any structure without this drainage will inevitably become an anaerobic mud bath during heavy rain.
Low-cost wicking beds
Our large beds are made from scaffolding or fencing cloth and wooden pegs as shown in the photo.
(Click here for Making low-cost-wicking beds.)

They  work well and have lasted six years so far without problems.

The plastic liner is still folded up and will be unfolded while the soil is shoveled in.

These beds are in a narrow shade house, unlike our standard shade houses.
We no longer use straw to line the sides.
Wicking beds near Woombye dug into a hill and made from logs. Note the drain holes in the form of black poly pipe drilled through the logs.
Wicking beds at the Gin Gin State Primary School. These beds are made from old railway sleepers. The site is on a slope. There are six small beds in each structure formed by sleepers which are stepped down. Each small bed is about 2m and is level.
We keep worms in all our beds, with very good results for our soil structure. www.KookaburraWormFarms.com.au sells worms and worm boxes designed to recycle kitchen scraps and weeds.

We also use plant pots, cut their bottoms off, place the pots upside down in the soil and use the saucers as lids. All our weeds, crop residues and kitchen waste are recycled through them.

Many people use sleepers and other good looking materials as shown below. We sacrificed looks for lower cost as we have 22 beds. We use scaffolding cloth and pegs.
All beds work equally well..