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.
Felslate
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 lets you mine ores while mounted.
You should also enchant your gloves with 
Enchant Gloves - Legion Mining.
Val'Sharah
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.
Suramar
Same as above, you will mainly find Leystone. Suramar is a level 110 zone, so you can't farm here at lower levels.
