Can I will away my HDB if my HDB Flat is a Short-lease 2-room Flexi Flat?

Yes, you can Will your Short-lease 2-room Flexi Flat as per any other assets in your Will.

Do note that for short-lease 2-room Flexi Flat, the HDB flat cannot be sold in the open market.

In the case where you Will the Short-lease 2-room Flexi Flat to your beneficiary, the beneficiary(s) will EITHER inherit the flat [subjected to HDB's approval (e.g. based on HDB's eligibility criteria for Short-lease 2-room Flexi Flat)] OR HDB will pay out a pro-rated sum of the original selling price based on the remaining lease of the flat to be distributed to the beneficiary(s).