considerably, dramatically, markedly, noticeably, sharply, significantly
Sales have slowed down quite markedly.

barely, hardly
The roadblocks hardly slowed them at all.

a little, slightly, etc.
gradually
eventually, finally
deliberately
She very deliberately slowed her steps.

down, up
Slow down a little!

begin to
try to
Rachel tried to slow her breathing.

be expected to
Economic growth is expected to slow.

seem to
Time seemed to slow down as she fell.

slow to a crawl, slow to a snail's pace, slow to a walk
I was nearing West Road when the traffic slowed to a crawl.

slow to a halt, slow to a standstill, slow to a stop
The two of them had slowed almost to a stop.

slow to a trickle
The flow of people into the building slowed to a trickle.

slow your pace
Bill slowed his pace to allow her to catch up with him.

be, prove, seem
remain

extremely, fairly, very, etc.
incredibly, remarkably
considerably, noticeably, significantly
My computer is noticeably slower than before.
He was noticeably slow to respond.
I was considerably slower than the other drivers.

a little, slightly, etc.
comparatively, relatively
agonizingly, desperately, excruciatingly, frustratingly, painfully, painstakingly
Filming was painfully slow.

notoriously
Civil court proceedings are notoriously slow.

at
They are extremely slow at reaching decisions.

slow and steady
She is showing a slow and steady improvement in her reading ability.

Slow is used with these nouns:
acceleration, accumulation, ascent, ball, bowler, bowling, breath, build-up, child, clap, climb, cooking, crawl, dance, dancing, day, death, decay, decline, deliberation, descent, deterioration, disintegration, drawl, drift, drip, erosion, evolution, footstep, fuse, gait, growth, jog, kiss, lane, leak, learner, march, melody, movement, onset, pace, passage, procession, progression, pulse, puncture, rate, reaction, reader, realization, recovery, reduction, response, rhythm, rise, service, sip, slide, song, speed, spin, spread, start, starvation, step, stride, stroke, subsidence, thaw, transition, tread, trickle, trot, walk, waltz, worker