What does "slip away" mean in this sentence?

[eggcracker]

I had seen sentences include "slip through" before I saw "slip away". So I can understand the sentences with "slip through". But I don't know the exact use of "slip", and I can't find proper explanation about "slip away" in the dictionary. The sentence confusing me is like this,"No longer these protohorses could slip away through thick forest when danger threatened." Give me some explanations about meaning of "slip away" above the sentence.
And I tried just two sentences to understand the "slip away" and "slip through".
Check these sentences below whether it's correct.
A.Sand particles slipped through my fingers.
B.Sand particles slipped away my fingers.
C.It keep slipping through my fingers.

 

[JMurray]

"No longer could these protohorses [STRIKE]could[/STRIKE] slip away through thick forest when danger threatened." Give me some explanations about the meaning of "slip away" in above the sentence.
Here, "slip away" means to leave or disappear from a place, usually quickly and without attracting attention.
For example: "I wasn't enjoying the party so I decided to slip away out the back door and go home".

If you think about how grains of sand can slip quickly and silently through your fingers, then you can understand how the protohorses might have slipped away through the forest in a similar manner.

And I tried just two sentences to understand the "slip away" and "slip through".
Check these sentences below whether it's correct.
A. Sand particles slipped through my fingers. (OK)
B. Sand particles slipped away through/from my fingers.
C. It keeps slipping through my fingers.


not a teacher

 

[eggcracker]

A. Sand particles slipped through my fingers. (OK)
B. Sand particles slipped awaythrough/from my fingers​

Does OK mean the sentence is suit to colloquial English? Or does it mean it's usually used?

 

[bhaisahab]

A. Sand particles slipped through my fingers. (OK)
B. Sand particles slipped awaythrough/from my fingers​

Does OK mean the sentence is suit to colloquial English? Or does it mean it's usually used?

It means it's normal usage.