Ice Slopes do not melt currently (as of R29 in February 2016) in hot biomes, not even on the Lava layer. So they can be used to make rinks and "Ice railways" to slide all over any Creativerse world powered by Fans.
If the environment is cold enough (which can be artificially managed by placing a number of Ice blocks together) Water or Bog Water can be dropped on cold blocks to make it freeze into Ice - infinitive if you let the liquid flow down from above where it should be warmer. As the temperature gets colder on high altitudes Water will also freeze there. Mind that wherever it's cold enough to freeze Water, also a freeze-scale will show up that will fill itself with white color, and upon being full will start to hurt the player-character with freezing damage over time.