1st Base Obstruction?

[jetemple25]

I had an 11/12yo youth game where a ground ball was hit to the second baseman who struggled with it. The 1st baseman (a fairly tall kid for that age) also struggled to get his foot on the bag. As he kept his eye on the fielder, awaiting the throw, his left foot jumped around a little and eventually ended up on the front right corner (foul territory towards home plate). At least that was the location stated in the offensive teams argument. His right foot ended up well in the dirt towards the outfield/2nd base side.

There was plenty of base to be had, but enough fielder leg in the way to cause the runner to slow down. This slowdown was just enough to make him late and out. I did not call OBS because from my angle as the home plate and only umpire, I thought the fielders foot was on the side of the base, perhaps even towards the back and not close to the front. It definitely was not in front of the base.

Either way, are both of these obstructions or not?

Thanks,
-Jet