Hi Michael
Marsh Mellow can be presented similarly to the way I present Marsh Mallow, using a baiting needle, thread say a 3ft length of multi-strand through the bait and tyre a loop in one end, pull the material back through the bait and as a stop, add a tough piece of grass, although modern carp anglers use bollies stops these days.
To the other end of your multi strand, attach a swievel. I prefer the 35mm film canaster, used like a bubble float, for casting , but fish this in-line, that is to say affix a plastic tube through the centre of the cannister, adding super glue to the base section, then add a tight sleeve of silicon rubber over the end of the tube, this will enable the swivel on the hook length, to be pushed into the cannister, this gives the effect of a floating bolt rig.
Say the last six inch of the multi-strand cast, add some vastaline or dry fly floatant to enable it to float, also put water in the canaster to assist with casting weight.
fire a few freebies out, and good luck?