I would sow them in a tightly covered tray(forming a mini greenhouse) placed somewhere receiving full sun for 2-4hours each day or in a humid greenhouse/hothouse that gets some hours of full sun and gets really hot. I try to germinate mine in my hothouse which can reach 60C in extreemly hot days and i got many(maybe even all...) Typhonium venosum to sprout in there plus a banana like baby which can either be Musa velutina,Heliconia rostrata or a ginger...
I am not very experienced germinating such plants though,my field are palm and cycad seeds which i sprout indoors! No luck with Musa velutina indoors for me though,even with bottom heat each day for 12hours to 30C and each night from a little lower to much lower...