Yes. However, you'll need to do the actual backdoor contribution and conversion process each year using your existing IRA accounts at your existing IRA custodian rather than using your Unchained IRA. Once the backdoor process is complete at your existing IRA custodian and the funds are sitting in a Roth IRA there, those funds can be moved to your Unchained Roth IRA in a Roth-to-Roth transfer using the Unchained IRA Transfer Form. Transfer less than the full amount to Unchained, even if only leaving $10 at your old brokerage, so that the brokerage does not close your IRA accounts and you can therefore use those same IRA accounts for the backdoor procedure in future years. If you have questions about backdoor contributions, please consult with your tax advisor, as Unchained cannot give tax advice.
Note: No contents of this blog may be relied upon as tax, legal, or financial advice, as they have not been tailored to you and have not been reviewed by any attorney, financial advisor, or tax professional. For any questions related to your own specific situation, please consult with your own attorney, tax professional, and/or licensed financial advisor.