Officialdom produced manuals on how to construct the various patterns of Flame Fougasse.  This is a diagram of a basic, roadside-installed model, that gives some idea of how simple the process was.  Best regards, JR.

Flame Fougasse blueprint.

Another Home Guard armoured car, based on a Sunbeam civilian automobile.  The UK Home Guard, nationwide, produced a wide variety of improvised armoured and other combat vehicles.  Whether many of these would have stood up to the assault of the Wehrmacht is, to say the least, doubtful.  Oh well.  Their presence was probably good for morale, in any case ... JR.

God wants me for a Sunbeam ...

In case there are any doubt about what a drum or two of tarry oil, an ignition charge and a length of corrugated iron could do - this is a photo of a Flame Fougasse test ignition in southern England, 1940.  Of course, since the Wehrmacht never arrived in England, this weapon was never used there.  However, it was used to some extent in the Italian and German invasions of Greece, where Flame Fougasses were installed by knowledgeable British troops against the advancing foe.  Concrete evidence of the results is patchy - but it has been reported that the physical and psychological effects on the enemy were substantial.  Not surprised.  Best regards, JR.