Seasoned Cast Iron NOT being Non-stick
Don't use flaxseed oil, it's one of the worst.

Something I only discovered recently is it's not just the smoke point you should be concerned about, it's the iodine number. This is important when it comes to the oil's polymerisation to make your coating. The lower the iodine number, the harder the resulting polymer finish. The smoke point should be used as a reference only for what temperature you should season at. If your oven can't reach the smoke point, pick an oil that it can.

To get the hardest, most durable surface you want an oil with the lowest value you can get. As this is actually coconut oil [about 8], you may not want to work with that aroma, so the lowest value odourless/flavourless oil is palm kernel oil [about 17]. You're probably good to a value of maybe 50 before things start to go downhill. The higher the iodine number the softer &amp; more sticky the resulting polymer is.

Flaxseed is about 200, literally at the other end of the scale. [It's not actually on that wikipedia list but you can search it independently].

As you currently have a soft layer, which may or may not be completely polymerised, I would suggest stripping it &amp; starting over. Once you have the correct oil, make sure you get your oven hot enough to polymerise the oil. You need to be above the smoke point - which means you need ventilation. Each layer takes an hour to 'bake' then at least an hour if not two to cool. You then repeat the process up to 6 or 8 times.  Your oil application each time should essentially be 'hardly enough to even tell it's there. Light, light coats &amp; repetition are the way. If it pools or drips, you will get an uneven result with soft areas that didn't fully polymerise.

After comments, refs:
This first is the one most people go to for 'proof' flaxseed is the best - but if you read the comments underneath you'll find many people get a sticky or flaking surface with this method. - Chemistry of Cast Iron Seasoning: A Science-Based How-To

Flaxseed is specifically mentioned as not recommended in this one - SeriousEats; How to Season a Cast Iron Pan (It's Easier Than You Think!)

Rumtscho's answer on What oil is best for seasoning a cast-iron skillet

For my final test - which I'll have to get back to you on - I'll be using either coconut oil [which I already have] or palm kernel [which I've yet to source] for a new pan I know I'll be opening on the * 25th *.
I'll let you know how it goes, compared to be previous attempts.