The bar under your server sums up what a build would do, for example Adds 4 roles, 2 sections and 6 channels. Press Build it and confirm, and the build plays in the picture of your server: each channel and role appears as the bot makes it, with a step counter and a running log beside it. A snapshot of your server is saved just before anything changes.
Deletions are always opt-in
Building never removes anything by default. When a design proposes deletions, or your server holds things the design does not, a Clean-up button appears beside Build. It opens the list with every box unticked and the note Deletions are off by default. Start fresh ticks them all at once so the rebuild matches the design exactly. Anything you tick requires a confirmation that the items and their messages are deleted permanently.
Items listed under Kept for your features are protected: they belong to features that are switched on (like open ticket channels) and deleting them would break the feature. To remove them, turn the feature off on the Services page first. A design that keeps your channels offers no clean-up at all.
Leaving things out
What gets built lists every planned change with its own checkbox. Uncheck a row and that one change is left out of the build; everything else still runs.
New-member onboarding
When a design includes onboarding, Onboarding screen under YourBot setup shows what it would set up, with a switch that stays off unless you turn it on. It turns on Discord's Community mode, adds a rules and a moderator-updates channel and configures the welcome screen and starter questions. This needs the bot to have Administrator. One step stays yours: the rules agreement gate is switched on by you in Discord's Server Settings, since bots aren't allowed to do it.
If some items fail
A build never stops halfway because one item fails; it finishes everything it can and then shows what didn't land and why in the Build report. The most common cause is a locked channel or a role above the bot. Drag the bot's role to the top of the role list or grant it access to the locked channel, then press Retry the failed items. Building again is always safe: anything that already exists is skipped, never duplicated.