Collocations for flexible - adj.

be, seem
become
remain, stay
make sth
We need to make the working day more flexible.

keep sth

extremely, fairly, very, etc.
completely, highly
infinitely
Human beings are infinitely flexible and able to adjust when survival depends on it.

enough, sufficiently

about
My mother is fairly flexible about what time I need to be home.

Flexible is used with these nouns:
approach, arrangement, attitude, framework, hour, instrument, packaging, plastic, schedule, stem, system, tube, wire, workforce