AnvilGUI.Builder builder = new AnvilGUI.Builder();
        ItemStack itemLeft = new ItemStack(Material.BARRIER);
        ItemMeta itemMetaLeft = itemLeft.getItemMeta();
        itemMetaLeft.displayName(Component.text("Cancel").color(NamedTextColor.RED));
        itemLeft.setItemMeta(itemMetaLeft);
        ItemStack itemOutput = new ItemStack(Material.GREEN_WOOL);
        ItemMeta itemMetaOutput = itemOutput.getItemMeta();
        itemMetaOutput.displayName(Component.text("Accept").color(NamedTextColor.GREEN));
        itemOutput.setItemMeta(itemMetaOutput);
        builder.itemLeft(itemLeft).itemOutput(itemOutput).title("Type flag arguments").plugin(plugin).text("");
        builder.onClickAsync((slot, stateSnapshot) -> CompletableFuture.supplyAsync(() -> {
            if (slot == AnvilGUI.Slot.INPUT_RIGHT) {
                return Collections.emptyList();
            }
            if (slot == AnvilGUI.Slot.OUTPUT) {
                action.accept(stateSnapshot.getText()); // Do whatever action I want with the string I fetched from the anvil
            }
            return List.of(AnvilGUI.ResponseAction.close());
        }));
        builder.interactableSlots(AnvilGUI.Slot.INPUT_LEFT, AnvilGUI.Slot.INPUT_RIGHT, AnvilGUI.Slot.OUTPUT);
        builder.open(activator);