Anyone can use this free tool to help run fair giveaways. It uses the next bitcoin block (not mined yet) to figure out the winner in a provably fair way. Just fill in the form and hit "Execute Giveaway" to get it started and the results come once the next bitcoin block is mined.
Results are sharable with the link at the bottom of the page (once you execute the giveaway)
Go to: https://bitcoinsbest.com/giveaway-manager.html