What you put into your will won’t determine who inherits your IRA. The same is true if you create a "living trust" to hold assets during your lifetime; the provisions of the trust won’t govern your IRA.
Instead, an IRA will be distributed according to the beneficiary designation form that you fill out when you establish the account. Therefore, you should be sure to fill out that form, naming primary and contingent beneficiaries. Check every couple of years to see if you want to make any changes.
You might want to leave your IRA to someone who is not capable of handling a large amount of money (or you might be naming a minor). If so, consult with an experienced estate planning who can help you set up a trust to inherit the IRA. Then your loved one can be the trust beneficiary and will receive funds at the discretion of the individual or institution you’ve named as trustee.