We demonstrate what we believe to be the highest efficiency obtained to date in a transversely diode-pumped ${\text{Nd}}^{3+}:\text{YLi}{\text{F}}_4$ slab laser operating at $1053\mathrm{nm}$ . The compact $11-\mathrm{cm}$ -long laser cavity configuration is based on total internal reflection of the intracavity beam at the pump facet of the gain crystal to improve the overlap with the pump radiation. Multimode operation with $9.5\mathrm{W}$ of output power and an efficiency of 45% is obtained for $21\mathrm{W}$ of pump power in a single-pass configuration. Using a second pass through the crystal and a new mode-controlling technique, the beam quality is improved to the diffraction limit with $6.9\mathrm{W}$ of output power and 33% of optical-to-optical efficiency.