s   ← "BOXKDQCPNAGTRETGQDFSJWHUVIANOBERFSLYPCZM"
Flt ← ⊂⊙↘₂⊃↙↘-⊸◿2⊸˜⨂ # remove block holding letter
{"A" "BARK" "BOOK" "TREAT" "COMMON" "SQUAD" "CONFUSE"}
≡⊂⟜⍚(◌◌⍥(⍥(⊙⊙⋅0)⊸≍⟜˜Flt⊙°⊂)◡⋅⧻ s ⊙1)