Yep, fats and fibre are not ideal post-workout because they slow down digestion.
Three teaspoons of flax a day should be fine provided you are also getting another healthy source of omega 6s such as ANPB or almonds.
A dietary ratio higher than 1.5 (omega-3) : 1 (omega-6) may lead to an omega-6 deficiency.
A better alternative to flax oil would be UDO's oil, as it contains a mixture of different oils (flax, sunflower, coconut, etc) and a ratio of 2 : 1 : 1 (omega-3 : omega-6 : omega-9)