This week's challengers tackle a complicated build--crafting a working oven from all natural materials, like sand, wood and water. Luckily, Callie North (Season 3), Clay Hayes (Season 8) and Am s Rodriguez (Season 7) are all highly-skilled former Alone participants. Can they complete what's normally a weeks-long build in just 3 days and with limited tools? Survival expert Britt Ahart (Seasons 3 & 5) will judge the results.