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Find your self a washing machine tub.
They are (/were?), stainless steel so last 'forever'
the myriad of perforations allow soil moisture in
and prevent large roots escaping.
Plant the fig with a gravel filled 2 or 3l soft drink bottle
with holes punched through the PET, off to one side of the drum,
with just the spout showing. This allows you to water
down into the roots in times of low rainfall.
that sounds ok, but i think the key to fruiting is to restrict the roots otherwise you will have a mahoosive tree with very few fruits. Plus you probably don't want a really big tree anyway