There is a statement in Mahabharata that refutes the idea that earth is flat in shape.
The bold portion of the following conversation between Vyasa and Kunti confirms that earth is not a flat body.
'Vaisampayana continued, 'Vyasa, the son of Satyavati, thus comforting
the Pandavas, led them into the town of Ekachakra. And the master also
comforted Kunti, saying, 'Live, O daughter! This son of thine,
Yudhishthira, ever devoted to truth, this illustrious bull among men,
having by his justice conquered the whole world, will rule over all
the other monarchs of the earth. There is no little doubt that, having
by means of Bhima's and Arjuna's prowess conquered the whole earth
with her belt of seas, he will enjoy the sovereignty thereof. Thy
sons as well as those of Madri--mighty car-warriors all--will
cheerfully sport as pleaseth them in their dominions. These tigers
among men will also perform various sacrifices, such as the Rajasuya
and the horse-sacrifice, in which the presents unto the Brahmanas are
very large. And these thy sons will rule their ancestral kingdom,
maintaining their friends and relatives in luxury and affluence and
[SECTION CLVIII, Hidimva-vadha Parva, Adi Parva, The Mahabharata]
Vyasa, while describing the earth, told that the earth contains seas as its belt. Thus, conforming that earth is not flat.