I mail little gifts and puzzles and reading materials to the seniors I work with as they isolate at home. These were fun but a bit stinky (toxic?)
I preheated my oven to 350°. Then I lined muffin tins with parchment paper. I assembled plastic faceted beads in each cup and heated for 18 minutes. I settled on 18 minutes because at 20 minutes they were melted to the point I need to drill holes. At 18 minutes there are the odd holes for strings.
I took them out of the oven and let cool for 10 minutes. They popped out of the pan easily. Then I pealed the parchment paper off.
I gathered the info for this project over several easy to find sites and YouTube videos. Some did the same procedure with pony beads, some used cake pans, some used higher heat.
I’d recommend 350°, lots of ventilation and checking the project in the oven every 5-10 minutes as different ovens, project sizes, bead brands and desired effect will effect the results.