Foamcore for the coffins themselves, definitely. As for the support, wood is definitely a good choice if you can find a type light enough. To get the angles you want, perhaps try PVC connectors?
DeviantART // Tumblr // Facebook // Instagram // YouTube
- Uniform (Little Witch Academia): ??% (Designing) Ellicott City 2017
- Paladin Armor Shiro (Voltron: Legendary Defender): ??% (Planning) ????
- Leo (FE: Fates) : ??% (Wig Styling) ????