1. Should you DIY?
Although theoretically one can write their will on their own in handwriting or download a standard doc from the internet, it's highly recommended you have it professionally drafted in a customized way which reflects the specific structure of your family and assets, and properly signed in front of two witnesses.
You wouldn't want to risk the will being legally dismissed or halachically challenged just because you weren't aware of the legal and halachic requirements!
2. So What is a Halachic Will?
So what is a Halachic Will? Is it a legal will or halachic document?
The answer is that it should be a proper legal will that is validated from a halachic perspective too. In other words, your will is structured like any other will, but will have extra clauses or a supplement (addendum) that makes sure that all the allocations are executed in a halachic manner that doesn't contradict the Torah Inheritance law.
3. Halacha Clauses or Halachic Supplement
How does the interplay work between the legal and halachic phrasing?
There are two available options, and as always: each has its advantages as well as potential downsides.
4. Option 1: Halachic Clauses
What most lawyers do is add at the end of the will a few "halachic" sentences or paragraphs that validate it generally.
These sentences usually define the allocations in the will as a gift while the person is still alive, thus bypassing the Torah inheritance which kicks in only when the person passes away.
A few things that should be taken into consideration when adding these clauses:
A. Make sure the halachic phrasing ("gift") doesn't contradict other clauses in the will which may include other definitions.
B. If the will refers to assets that are abroad, the local registrar may not understand the halachic phrasing, or may even consider the allocations as a gift – instead of inheritance - from a legal perspective too, which may have tax implications.
That being said, since in Israel this is a common practice, the registrars are familiar with these types of wordings, and it usually doesn't cause any complications.
5. Option 2: Halachic Supplement
The alternative to the above is to have a halachic supplement which is physically a separate document from the legal will.
The halachic supplement will include all the necessary halachic instruments which will validate the will.
The halachic supplement has two main advantages:
1. It isn't needed for probate.
In other words, when the will needs to be used (after your 120) the halachic supplement doesn't need to be presented to the legal authorities, thus saving a potential mix up with legal officials trying to decipher halacihic phrasings.
The only case in which the halachic supplement would have to be practically used would be if G-d forbid the halachic heirs (i.e. sons) would dispute the legal will in a Din Torah. In that case the halachic supplement would be presented in order to prove that the legal will was properly executed from a halachic perspective too.
2. Covers several wills.
Since the halachic supplement is a separate document, it can cover multiple wills. So if, for instance, you have an Israeli will for your Israel assets and an a US will for your assets abroad, you can draft one halachic supplement that will halachically cover both wills.
6. Where do you put the will? Who keeps it?
Back in the pre-digital days, people used to have their lawyer keep the will for the family. Albeit in today's day and age, who knows where the lawyer will be when we're not around anymore.
There is no obligation to deposit your will. Once it's signed in front of two witnesses it's absolutely valid even if not deposited at all.
Mose people keep the wills and halachic supplement in a safe place in their home, together with all the other important documents (such as passports, nirth certificates etc.).
In Israel, the Inheritance Registrar gives you the option to deposit your will in the registrar's office, thus making sure it doesn't get lost or misplaced. The only thing to remember is that if you decide to write a new will in the future, you should take out the "old" will and deposit the new one instead of it.
Needless to say, if you signed a separate halachic supplement to the will, the supplement should not be deposited to the registrar. It will still serve as documentation to the fact that your legal will was halachically executed, and if needed can be used in a Din Torah if the halachic heirs were to challenge the halachic validity of the will.