Place the peeled, sliced carrots in a large pot and add enough water to cover them. Bring to a boil over high heat, then reduce to a simmer and cook until just tender when pierced with a fork, about 8–10 minutes. Drain the carrots and set them aside.
Return the empty pot to the stove over medium heat. Add the butter and melt, stirring to prevent browning.
Add the brown sugar to the melted butter and cook, stirring, until the sugar begins to dissolve and the mixture is smooth, about 1–2 minutes.
Stir in the orange juice and the orange zest. Cook, stirring occasionally, until the mixture is bubbling and slightly thickened, about 2–3 minutes.
Return the drained carrots to the pot and toss gently to coat them evenly with the orange glaze. Cook for 1–2 minutes more to heat the carrots through and reduce the glaze to your desired consistency.
Transfer the glazed carrots to a serving dish and toss with the craisins/dried cranberries and the toasted, chopped walnuts, if using. Serve warm.