According to Wiktionary's conjugation table (below captured in portions), it would appear that appe- in the imparfait forms is one syllable (/a.p/, or strictly speaking one syllable and the consonant sound of the next syllable) except in the first and the second person plural, wherein it is two syllables (/a.pə/).
But on the present tense first and the second person plural, the same table assigns but one syllable to appe-.
On Forvo.com too, appe- seems to receive one or two syllables on a rather random basis. For example:
For j'appelais, Domigloup /a.pə.lɛ/, gwen_bzh both /a.pə.lɛ/ and /a.plɛ/.
For appelait, /a.pə.lɛ/.
For l'appelait, /a.pə.lɛ/.
For nous nous appelons, spl0uf /a.plɔ̃/, huntmdwn /a.plɔ̃/, gwen_bzh (probably) /a.pə.lɔ̃/, Domigloup /a.pə.lɔ̃/.
The question is then: Based on the above data, am I OK to conclude that I am free to give one or two syllables to appe- as occurring in these forms of appeler?