Things you would need:

• Ikea side table
• Wooden legs (height depending on how high you want the ottoman)
• Spray paint
• Home decor Fabric
• Foam (atleast 3-4″ thick)
• Batting 
• Upholstery stapler gun
• 4 Heavy duty top plate
• Spray adhesive which can stick foam
• Simple screwdriver

Method:

Prepare legs. Spray paint them outside and keep them to dry overnight.

1. Remove the legs from the ikea table
2. Clean the table surface
3. Cut the foam same size as the top of the table
4. Cut batting atleast 4 inches more on all sides.
5. Mark on all 4 sides where the legs would go. Leave enough space for fabric to come in.
6. Screw in top plates at equal distance from all sides
7. Now you can upholster the ottoman by putting batting on top of foam and stapling it towards the back
8. On top of this put the fabric and repeat stapling part.
9. Now you can screw in the wooden legs.