The High elves base set contains both square and round bases
Namely:
square:
20x20mm (90 bases)
25x25mm (55 bases)
30x30mm (40 bases)
40x40mm (19 bases)
50x50 (15 bases)
75x75mm (10 bases)
100x100 (8 bases)
25x50mm (22 bases)
30x60mm (20 bases)
40x60 (10 bases)
50x75 (11 bases)
50x100mm (11 bases)
60x100mm (10 bases)
100x150mm (2 bases)
round:
25mm (42 bases)
32mm (42 bases)
40mm (19 bases)
50mm (14 bases)
60mm (12 bases)
75mm (7 bases)
100mm (3 bases)
35x60mm (16 bases)
52x90mm (5 bases)
92x120mm (3 bases)
Bases doesnt nedd any supports. Just print them with their flat bottom faced towards building plate