Correct spelling, explanation: the base form of facing is face and it is a word that comes from the Latin form facies, which could be translated as form, face, or appearance. Later, facing also appeared in Old French, and then, in Middle English, it finally entered the English language. Today, facing has the function of a noun or is a common prefix.

Definition of facing:
1. noun – an extra layer of material,
She looked really elegant at the meeting in that white jacket with a blue facing.
2. suffix – turned towards a particular direction,
Most skiing accidents happen on north-facing slopes so be careful while skiing there.
3. verb (the present participle) – the fact that you have to deal with a problem,
Facing the problem, she decided to talk to her boss and tell him about everything.

Collocations with facing:
A few popular collocations with facing include: customer-facing (direct consumer service), east-facing, and south-facing.
To make your company more friendly, you need to improve your customer-facing.
The east-facing bedroom of the house is spacious, bright, and really warm.
The south-facing part of the garden provides the best fruit as there is a lot of sun there.

Incorrect spelling, explanation: facing comes from face and the rule says that when you add an -ing ending to a word that ends with an -e letter, you need to remove this -e letter. A number of English speakers forget about that and they often spell facing as faceing, which is an incorrect form.

Incorrect spelling