Here is one way to make a cone from flat stock. I used aluminum sheet coil but you could use paper or any flat material. You can find cone calculators online, I used this particular cone calculator ... ...
by RICHIRA decor
by NUR ART
by Ruhee's Crafts and Arts
by Crafty Ladybug
by DOLLS DRAWING & PLAYING
by Kids Drawing Ninja
by 365SKETCHES