布 + directional
下 = 'lay out / put down'. Common collocations:
布下天罗地网 'set an inescapable net',
布下陷阱 'set a trap',
布下重兵 'station heavy troops',
布下迷魂阵 'set a confounding formation'. The
下 is a result complement, not a separable particle, so the object follows:
布下 + N.