help with custom recipes

[wanton sonnet]

my skript for custom boots is not working for some reason

    register new shaped recipe:
        id: "custom:Slime Boots"
        result: diamond boots named "&aSlime Boots"
        shape: "ccc", "bcb", "aca"
        group: "bloop"
        category: "building"
        ingredients:
            set ingredient of "a" to slime block of flame 1 named "&fCoagulated Slime Block" with all flags hidden
            set ingredient of "b" to slime ball
            set ingredient of "c" to air```

[fluid sedge]

if you're using an updated skript/skbee version, the all flags hidden syntax has changed to with all itemflags