Although lures have a practical aspect, it's not the practical aspect that attracts anglers, but the idea of successfully deceiving fish... So, even for species traditionally fished with bait, the lure angler will always be looking for a way to bypass conventional fishing.

Less yield but a winning bet
While the sponge is obviously less effective than a real piece of bread, it does offer a few advantages, such as a perfect hold on the hook, but above all the satisfaction of having succeeded in deceiving a fish's distrust and catching it in a different way.
Identical assembly
Sponge fishing and bread fishing are fundamentally the same, and as such, the equipment, rigs and spots are all the same. It's simply the philosophy and strategy that change!

A basic piece of sponge
So on your 6 hook, your piece of fresh bread is simply replaced by a conventional piece of sponge measuring approximately 1.5 cm x 1.5 cm x 1 cm. Ideally, you'd like to cut a piece with the shape of a real piece of bread.
2 useful tips before you start
To cast far, first wet your sponge, then wring it out. Then, to keep your line perfectly buoyant and remain as unobtrusive as possible, you can grease your nylon (or fluorocarbon) leader the way fly-fishermen do.
In the same spirit, you could soak it with an attractant if the bites are too slow in coming!

Create a real business
Luring a carp with a piece of sponge means really fooling it. Carp will gobble up this inert lure without any animation, so you'll need to create a real feeding activity and bank on carp actually mistaking this lure (of the same color and shape) for the real piece of bread it's meant to imitate.
Then bait your spot copiously with numerous pieces of bread and wait for the carp to arrive in numbers and gobble regularly. Once a competition or feeding frenzy has set in, it's time to cast.
To place your sponge, choose the area where the greatest number of gobbles occur and wait for a carp to make a "mistake". Be vigilant and strike as soon as the line becomes taut!

A whisk or imitation bread for fly fishermen
For fly-fishing enthusiasts, it's possible and even fun to use your "reservoir" rod and even create bread imitations. So grab your vises!