A trail starting from Agios Athanasios, crosses the mountain from east to west, leading close to Koubi peak. The fastest route to Psili Korfi is via a path that begins just after an abandoned open quarry, on the way to the villages Agios Charalambos and Agia Triada (the road intersects with the main road connecting the town of Karpenisi to Lamia; you will see it on your left if you’re leaving from Karpenisi). In the winter, bring snow chains with you, as the road is often buried in snow.
A map is essential, as the path’s opening is not easy to spot. Begin your ascend on a steep slope, heading southwest and keeping Koubi peak on your left, until you reach the mountain’s ridge,offering a panorama of Karpenisi/ Spercheios valley. Then head west, following the ridge. Alternatively, keep the ridge to your right until you come across the gully and then begin your ascend from the right side. The final part of the route is quite steep, while the snow is often frozen; in the winter, you should not attempt it without crampons and an ice axe.

Source: mountainsgreece.com