These are made at exactly the same place. The second is heavy: the back of the tongue lifts and the sound fills the mouth.
تTa
The tongue tip and tooth roots
The tip presses against the roots of the upper front teeth — where the tooth enters the gum — and cuts the air off. Ṭāʾ, dāl and tāʾ are all made exactly here.
طTaa
The tongue tip and tooth roots
The tip presses against the roots of the upper front teeth — where the tooth enters the gum — and cuts the air off. Ṭāʾ, dāl and tāʾ are all made exactly here.
Both come from the same place in the mouth — what changes is how the tongue is held, not where it touches.
Two words, one letter apart
Everything else in these words is identical. If you can hear which is which, you have the letter.
تِين
tīn
figs
طِين
ṭīn
clay