Could someone please give me a phonetic pronunciation for the following sentence (Ulster pronunciation preferred, but not critical):
Trí na chéile a thógtar na cáisléain

Also, if anyone has the IPA pronunciation (as an addition to the phonetic) I would love that. I'm writing a glossary for a fictional work.

Many thanks!

I'm familiar with:
de réir a chéile a tógtar na caisleáin

trína chéile means "through each other", but seems to me to be Béarlachas as it doesn't mean "through dependence on each other", but rather "through each other" in the sense of "through holes in each other's bodies".

Why is it confused (trína chéile) that the castles are built?

I’d say:
De réir a chéile a thógtar na caisleáin
/dʲə ɾʲeːɾʲ ə çe(ː)lə hoːgtəɾ nə kaʃlanʲ/

or
I ndiaidh a chéile a thógtar na caisleáin.
/ə nʲeːj ə çe(ː)lə hoːgtəɾ nə kaʃlanʲ/

I’m no expert for Ulster Irish. So I can’t tell which one would be used there.

/dˠə ˈɾˠeːɾʲ ə ˈçeːlʲə ˈtˠoːgˠtˠəɾˠ nˠə kˠiˈʃlʲaːnʲ/

or simplified without showing velarisation as:

/də ˈɾeːɾʲ ə ˈçeːlʲə ˈtoːgtəɾ nə kiˈʃlʲaːnʲ/

And for "i ndiaidh a chéile":

/nʲiə ˈçeːlʲə ˈtoːgtəɾ nə kiˈʃlʲaːnʲ/

Some pre 1950 speakers would have had /ˈtoːgəhəɾ/.

Sure! Please share the Irish sentence you’d like me to give the phonetic pronunciation for, and I’ll write it out clearly using English-style phonetics.