Can I use corn flour instead of starch to remove oil from a pair good leather boots?

Corn flour won't be as effective as starch for removing oil from leather. There are some alternative methods you can try:

1. Baking soda: Apply a generous amount of baking soda onto the surface, then wait until it has completely covered the oil spot. After, gently wipe the baking soda using a clean cloth while brushing at the stains and spots.

2. Salt: Apply a generous of salt and let it rest for sometime (30 or more minutes is best). Brush off.