Use the Extra Small Flat Magnetic Flight Stands for your Hellions.
[Buy Product=warhammer-40k-medium-sall-flat-jetbike-stand-posable-magnetic-flight-stand,Variant=All]
For the flat bottomed clear skimmer base that comes with the kit, use the 32mm self-adhesive magnets
[Buy Product=flexible-self-adhesive-magnets,variant=32934330269780]
For a set of replacement bases with preset magnet holes, use these bases with magnets.
[Buy Product=bases-premagnetized-warhammer,variant=32508936716372]
To magnetize the weapon options, use 2mm x 2mm x 1mm block magnets.
[Buy Product=100pcs-2mm-x-2mm-x-1mm-1-16x1-16x1-132-block-magnets,Variant=All]