Pronunciation: [hˈe͡ɪslət] (IPA)
Correct spelling for the English word "hastlet" is [hˈe͡ɪslət], [hˈeɪslət], [h_ˈeɪ_s_l_ə_t] (IPA phonetic alphabet).
See Haslet.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.