If Wales was flattened out...

This is about a map projection that maps all surfaces as if flat, measuring distances down to those between atoms on solid and liquid materials exposed to the atmosphere. It has some interesting consequences, reminiscent of the Hitch-Hiker's Guide To The Galaxy:
All well-known places on the map are far apart, and unless the map is very small scale it would usually be blank. Surfaces fluctuate in size, water more than land. Surfaces made discrete particles vary quite dramatically so their area changes with the weather. Windblown sand and soil particles mean dry surfaces alter in area. Flooding involves the shrinkage of the submerged area rather than its growth. Tides and waves cause unpredictable fluctuation in the length of strands and coastlines.
Other consequences:
Any area bounded partly by coastline, lake or river has a very long border, but any artificial borders are relatively very short, for instance most of the border between the US and Canada.
Arid areas have relatively larger and more easily determined areas than humid ones.
Hilly areas are relatively larger than flat ones, so for all we know, Andorra is bigger than the Netherlands.
The size and roughness of the particles composing the surface strongly influences its area, so a dried up delta is bigger than a pebbly beach of the "same" size, but a wet delta is much smaller.
Vegetation is also important. Deforestation, along with mowing the lawn, drastically changes the area of a region. Therefore, it may be that countries chopping down rainforests reduce the size of their territories, and leaving an area to go to scrubland enlarges it.
Annexing a country can reduce the length of its border while increasing its area.
The population density of any territory is close to zero persons per square kilometre. Its rainfall is also very low considered in those terms. Certain places are deserts even in the middle of a rainforest. In temperate regions, time of year has a stronger influence on hours of sunlight per unit area because of the length of shadows, and sunny dusk is relatively less significant than sunny noon.
Landlocked powers invading island nations hugely increase their border length.
Distances between two officially named points on a map are very large. The only imaginable distances are between almost entirely unknown points, such as two soil particles in one's back garden. Other distances are inconceivably huge.
Rivers are very long.
Latitudes and longitudes tend to change irregularly, so the location of any point on the map is unpredictable, both in general and through time.
The highest and lowest points vary, as do altitudes generally. Mining and building tend to increase the area of a region unpredictably. Opening and closing windows and doors alter the sizes of built-up areas. Hence suburbs get bigger in summer and smaller in winter, but business areas vary less in size.
Finally, on a slightly different note, since the territories extend to the centre of the Earth, every administrative unit has a border with every other there at a point. The volume of these wedges gives a more realistic estimate of the size of the region than their true area.