We put out the large round keep blocks plus some mineral blocks. When I can get them I use those natural salt licks too.
They are best off the floor, on a rock or concrete if poss.
I use big mineral salt licks, and this year the buggo lick off the floor in the field. The downside is that the licks kill the grass, so if at livery, might be worth checking with YO first.
I have also tried D&H pasture lick and horselyx this year. Both all well and good, but end up with brown nosed horses and you have to tip them out after rain.
i use the dodson and horrell vitamin and mineral block which they love. it comes in a big bucket. uniblock .found some ie horselyx too sweet and they gorged on them so just for treats.