Step 1: Distribute 2 L of clean, potable drinking water to every person, every day, at no additional cost to them.
Step 2: Distribute 2200 kcal of nutritionally adequate food to every person, every day, at no additional cost to them.
Step 3: Allocate 20 m^3 of private, secure shelter to every person, with right-of-occupation intervals lasting no less than 4 years, at no additional cost to them.
Step 4: Allocate ~350 L/day for treated water and sewer lines--sufficient for cooking, cleaning, hygiene, and sanitation--to every person, at no additional cost to them.
Step 5: Distribute 800 W of electrical power to every person, at no additional cost to them.
Step 6: Allocate 50 Mb/s data network bandwidth to every person, at no additional cost to them.
Step 7: Build sufficient additional public infrastructure for transportation, healthcare, business, and recreation, such that a reasonable amount of use of those commons is available to every person at no additional cost.
Step 8: Distribute a quantity of spendable currency to every person, with no requirements for eligibility or restrictions on its use.
Starting at step 8 is, in my opinion, a recipe for inflation and rent-seeking.
UBI is, in essence, an attempt to create a mixed economic system that is communist at the bottom end and capitalist at the top end. If you do not establish the minimum quality-of-life boundary by producing or taxing-in-kind the required goods and services as an inherently governmental (+ non-profit NGO) function, the rent-seekers in the upper class can and will capture some of the benefit intended for the lower class, and possibly enough of it that the lower class can no longer solely subsist upon it.
If the subsistence-level of existence is guaranteed, there is no longer any leverage provided to a person with more resources by virtue of the poorer person needing to accept a bad deal in order to live, while the richer person can walk away from the table without meaningful consequence. Workers cannot be as easily exploited if everyone can afford to quit their jobs. Renters can always fall back to their sleeping cubicle.