An altar is any structure on which offerings such as sacrifices are made for religious purposes. It was usually a raised platform with a flat surface.
An altar always represented a place of consecration.

Espacios domésticos destinados al culto: Aedicula dentro del ámbito del hogar hace referencia a un pequeño templo con dos partes diferenciadas, el templete y su basamento. El primero formados por columnas o pilastras con un espacio cerrado. El segundo, el basamento, macizo y de forma rectangular o cuadrada con un nivel suficiente para acceder a ella. Ricamente decorado con pinturas figurativas de mayor o menor complejidad, también es frecuente utilización de
relieves de estuco. Se descubrieron otro tipo de Aedicula de madera, tiene un carácter híbrido, la parte superior con características de un templete y la parte inferior, denominada aediculae de obra suele ser un basamento macizo, donde se guardaba imágenes como instrumento de culto.

https://www.studocu.com/es/document/uned/historia-de-la-cult...

--------------------------------------------------
Note added at 1 hr (2023-12-08 14:46:00 GMT)
--------------------------------------------------

Furthermore, the lararia are classified into three different types, according to George
Boyce: the wall painting, the niche, and the aedicula, although sometimes several
types appear in combination.

----------------------------------------------------
The aedicula type resembles a miniature temple, which is situated on top of a masonry podium, and may also be decorated with painting.

https://core.ac.uk/download/pdf/213389088.pdf

For example, statuettes of tutelary divinities were placed inside the niches on street façades or onto the masonry shrines built into the wall or floor of a household’s atrium, alongside the figures of snakes and Lares typically painted
there (Fröhlich, 1991).

https://oro.open.ac.uk/79388/1/79388.pdf

Lararia (alsocalled sacella [singular: sacellum]and aediculae [singular: aedicula]) are shrines to the household gods found in many Roman houses. They were located in atria, gardens, courtyards, and/or kitchens. Depending on the wealth of a household, the lararium could be a free-standing shrine, a wall niche, a cabinet, or a fresco. They sometimes accomodated statuettes of the Lars (protectors of the household), the genius (guardian spirit) of the paterfamilias, the juno (guardian spirit) of the materfamilias, and deities with special meaning for the family.

https://oro.open.ac.uk/79388/1/79388.pdf

Aedicula (plural, aediculae)
A small shrine enclosing a niche for a statue. An aedicula often consists of a pediment resting on a pair of columns.

http://www.art-and-archaeology.com/roman/glossary.html


I think I would use 'masonry lararia (aediculae)'.

--------------------------------------------------
Note added at 5 hrs (2023-12-08 18:02:56 GMT)
--------------------------------------------------

In the northwest corner of the portico a masonry aedicula lararium formed an arched niche on top of a solid podium. A low wall connected the columns and pillars of the portico.

https://roman-gardens.github.io/province/italia/pompeii/regi...

Noun
basamento m (plural basamentos)

the base of a column or another structure, plinth

https://en.wiktionary.org/wiki/basamento

--------------------------------------------------
Note added at 5 hrs (2023-12-08 18:35:39 GMT)
--------------------------------------------------

Their cult was materially located at the so-called lararia, household shrines composed of a niche or masonry aedicula, sometimes with a separate altar in front, where the worship of the other domestic deities also took place. The word lararium is rare and first appears only in the Scriptores historiae Augustae; before that period, the domestic shrine was simply called sacrarium or sacellum. But lararium will be used in this book by several writers as a conventional term to describe such household shrines.

https://irfrome.org/wp/wp-content/uploads/2021/07/acta49.pdf

I've changed my mind and I think 'masonry aediculae' would be better. Aediculae are a type of lararia, which are shrines or chapels for household gods. I'm pretty sure that 'de obra' means that they were purposely built structures.

--------------------------------------------------
Note added at 1 day 5 hrs (2023-12-09 18:47:40 GMT)
--------------------------------------------------

Where I live in Spain, 'de obra' means made of bricks: a fence, a wall, etc. However, in this case, I wanted to know what 'aediculae de obra' looked like, whether they were free-standing or a niche in a wall, but after spending about an hour on this question, I was no nearer the answer. If I'd been able to find a decent reference, I would have posted my suggestion.