The spelling of the word "stacking ups" can be confusing since it is not a commonly used phrase. However, it can be phonetically transcribed as /stækɪŋ ʌps/. The "ck" in "stacking" represents a voiceless velar stop, while the "ing" at the end is pronounced as a nasal sound. The "ups" in the end is pronounced as a close back rounded vowel (ʊ) followed by a voiceless bilabial stop (p). Therefore, the word is pronounced as "stak-ing ups."