Do the allies could built a boat of ice?

Yes, the idea of building a boat from ice, while impractical for long-term use, is theoretically possible. Ice can be shaped and formed into structures, and there have been historical instances of ice boats used for transportation over frozen surfaces. However, for practical maritime use, ice would be too fragile and susceptible to melting in warmer conditions. Therefore, while it can be done in specific contexts, it is not a viable option for conventional boat-building.