This Felslate farming guide will show you the best places for mining [Felslate]. You can mine this ore from Mining skill 1, you will get the same number of ores as if you had mining skill 100.
If you are revered with Valarjar, you should get the [Boon of the Salvager] enchant from Valdemar Stormseeker at Stormheim. It allows you to sometimes loot [Salvaged Armor] which can contain extra Felslate or Leystone Ore.
Legion introduces three new items that you can use to speed up farming ores. These three items are: [Leystone Hoofplates], [Demonsteel Stirrups], [Stonehide Leather Barding]. You should use these if you can find them cheap on the Auction House, or craft it yourself if you can.
Every mobs scales to your level in Legion, so it will be a lot harder to avoid the mobs attacking you while you try to farm ores. The combination of these three will make farming ores a lot easier, but the one I would recommend the most is [Demonsteel Stirrups], which let's you mine ores while mounted.
You should also enchant your gloves with [Enchant Gloves - Legion Mining].
This is best place to farm Felslate. There is always a few Stoneblood Basilisk up at the marked area, so you should have no downtime. You can mine the basilisk after you kill them and they drop Felslate.
Similar to the previous place, but the basilisk are a bit more spread apart. There is always a few Felfire Basilisk up at the marked area, so you should have no downtime.
If for some reason you can't farm at the two previous places above, then you can also try mining Felslate. But it's a rare spawn of Leystone, so you will mainly find Leystone.
Same as above, you will mainly find Leystone. Suramar is a level 110 zone, so you can't farm here at lower levels.