Read and re-read yet I'm still baffled; if you think a BMS, which I'll assume is the acronym in question, is going to prevent the runaway condition, you are sorely mistaken. But thank you for questioning my reading comprehension; I'll question your battery charging comprehension instead, since this is a technical discussion.
The vast vast majority of 3S packs (e.g. hobby RC packs) have no in built BMS and so the advice suggested (4V constant voltage with resistor per cell) is very dangerous for inexperienced users. If they DO have a proper balancing BMS this may work, however it will need to be close to the protection circuitry that for example a laptop battery offers.
You will still need to provide protection in the case of 2.8V/cell or less. Many battery protection circuits DO NOT isolate the battery from charging currents when the battery is under-voltage; the reason for this is to allow the battery to be recovered by an appropriate charger, which is usually possible down to about 1.5-1.8V/cell with some deterioration in the capacity if the charge is replaced very slowly. The exceptions are things like power tool batteries, because users are idiots and will try anything to recover their 100 euro battery that they left discharged, these tend to prohibit almost all zero volt charging as the terminals are too tempting to hook up to some external source. But I can confirm that the majority of BMS circuits will not block charging below 2.8V; for instance, the BQ20z70 device used in a great deal of laptop batteries allows zero-volt charging, and it applies no special current limit in this case; neither do common single-cell Li-Ion isolators like AP9221 or the venerable DW01 which is seen in pretty much every cheap single cell protected Li-Po. There are a few laptop batteries with pyrofuse devices like 12AH3 which can semi-permanently isolate the pack if it's gone below a certain voltage. Again, quite rare, and usually only seen in very high volume consumer kit.
Therefore, I continue to insist that you should not recommend charging any Li-Ion battery pack with only a voltage source and resistor. It really is very little extra cost to use a proper Li-Ion charger chip and protection circuit, and offers a significant improvement to the safety of the system. The danger, as ever, is that advice is copied by those who have no appreciation for the danger that Li-Ion batteries pose, and then implement chargers like this thinking it's perfectly sufficient.