The best way to do it with stock grants is to sell the stock as soon as it vests and invest the proceeds in accordance with your preferred AA. But it sounds like you have not done that.
If you want to sell the stock now, the usual capital gains tax rules apply - if you've held the stock for less than a year, any gains are taxed as regular income, if over a year, you pay long term capital gains tax. The starting value is the value as of the vesting date.
Check the lots you own and determine if they are short term or long term and how much you have in gains for each lot. Then you can come up with an exit plan that minimizes taxes.